bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary fractionation by gel electrophoresis of the membrane proteins and lipoproteins of Halobacterium halobium
Authors: Brown A. D. , Pearce Robyn F.
Published: December 2009

Lipoproteins and the corresponding defatted proteins from the membrane of Halobacterium halobium were fractionated by electrophoresis in polyacrylamide gels in the presence of urea. The lipoprotein mixture was resolved into 17–20 bands of which one was free of lipid and accounted for about 15% of the mixture. Most or all of the remaining 16–19 bands were tightly associated with lipid and at least one of them contained a complex mixture of lipids. There is evidence that some lipoprotein fractions were formed from others by aggregation or disaggregation. There were changes in the proportion of some lipoproteins during a growth cycle of the organism. The changes were correlated with changes in lipid composition of the membrane but not with changes in the amino acid composition of the mixture of membrane proteins.
Effect of adrenalectomy and hypophysectomy on responses of rat liver enzymes to high-fructose diets
Authors: Freedland R. A.
Published: December 2009

The effect of dietary fructose on the activities of a number of enzymes was studied in normal, adrenalectomized, and hypophysectomized male Sprague–Dawley rats. The effect of feeding a high-fructose diet on relative liver size, soluble protein, glycogen, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucomutase, glyceraldehyde-3-phosphate dehydrogenase, and glucose-6-phosphatase was not appreciably altered by endocrinectomy. It appears, therefore, that the fructose effect on these rat liver constituents is not mediated by adrenal or pituitary hormones, although endocrine function may influence enzyme activity. The enzymes which were not particularly affected by either endocrinectomy are those associated with the metabolism of phosphorylated intermediates.The fructose diet increased the activities of L-α-glycerophosphate dehydrogenase and lactic dehydrogenase to a greater extent after endocrinectomy; therefore, an inhibition of the fructose effect in normal animals by endocrine function was postulated. The effect of feeding fructose on the activities of the pentose-phosphate-metabolizing enzymes and glutaminase was abolished by hypophysectomy. In this case it was postulated that pituitary function is required for the fructose effect as a permissive agent. The fructose-mediated increases of malic enzyme and uridine-diphosphoglucose dehydrogenase were diminished in magnitude after endocrine removal, but not abolished.The activities of the urea-cycle enzymes, transaminases, and serine dehydrase were not increased by fructose feeding. The relationship between the fructose effect and endocrinectomy appeared to be complicated in the case of malic dehydrogenase and fumarase.
Hyperphenylalaninemia: the effect on cerebral amino acid levels during development
Authors: Lowden J. A. , LaRamée M. A.
Published: December 2009

The subcutaneous administration of phenylalanine to adult or 20-day-old rats produces a 20- to 25-fold rise in cerebral phenylalanine with only a two- to five-fold rise in tyrosine.The branched-chain amino acids decrease in the brains of these animals but levels of nonessential amino acids are unchanged.In 10-day-old rats subcutaneous phenylalanine administration produces a greater increase in cerebral phenylalanine and tyrosine and has less effect on the branched-chain amino acids, but causes marked decreases in nonessential amino acids. The findings suggest that the permanent defect in myelin formation produced by hyperphenylalaninemia in the newborn rat may be related to altered intermediary metabolism resulting from the fall in nonessential amino acids.
Pyruvate kinase: modulation by L-phenylalanine and L-alanine
Authors: Vijayvargiya R. , Schwark W. S. , Singhal R. L.
Published: December 2009

L-Phenylalanine was found to be a competitive inhibitor of pyruvate kinase in the rat prostate, seminal vesicles, uterus, and skeletal muscle. In contrast, L-alanine exerted no appreciable effect on pyruvate kinase activity but was capable of protecting against, as well as reversing, the inhibition produced by L-phenylalanine. The results suggest that the interactions between L-phenylalanine and L-alanine are important to the regulation of pyruvate kinase activity in tissues containing the M-type isozyme.
The metabolism of formycin, an adenosine analogue
Authors: Caldwell Ian C. , Henderson J. Frank , Paterson A. R. P.
Published: December 2009

Formycin, a C-glycoside analogue of adenosine, is rapidly converted to phosphorylated derivatives by Ehrlich ascites tumor cells in vitro. In the presence of an adequate energy supply, the 5′-triphosphate was the major phosphorylated metabolite of formycin; under some conditions, high levels of formycin 5-monophosphate and 5′-diphosphate also accumulated in the cells. In most experiments, the concentration for formycin phosphates approached that of the adenosine phosphates. Formycin was also extensively deaminated to the corresponding inosine analogue, formycin B; the ratio of deamination to phosphorylation was approximately 5. When formycin was administered to mice bearing the Ehrlich ascites tumor, formycin phosphates were detected in extracts of the tumor cells; again, formycin 5′-triphosphate was the major nucleotide metabolite.
Mode of action of choline. IV. Activity of the enzymes related to fatty acid synthesis and the levels of metabolic intermediates in choline-deficient rats
Authors: Chalvardjian A.
Published: December 2009

Three groups of choline-deficient (c.d.) and choline-supplemented (c.s.) rats were fed, respectively, a fat-free, a moderate (7%), or a high-fat (31.5%) diet for 3 days. Further groups of c.d. and c.s. rats on the 7% fat diet were killed at intervals of 2, 3, 4, 5, 8, 11, and 15 days. (1) The c.d. rats on the 7% and 31.5% fat diets developed fatty livers. (2) The activities in the liver of the enzymes related to lipogenesis were increased slightly in the initial stages in c.d. rats fed the 7% fat diet over their c.s. controls; but, by the end of 15 days the mean activities of the enyzmes were greater in the c.s. controls, indicating a diminished response of the c.d. livers to dietary challenges. (3) The hepatic levels of total adenine nucleotides and ATP were lower in the c.d. than in the c.s. rats fed the 7% and 31.5% fat diets. Increasing the levels of adenine nucleotides and ATP by feeding adenine sulfate did not prevent fatty liver in the c.d. rats fed a 7% fat diet. (4) Fatty acid oxidation, as assessed indirectly by the cytoplasmic NADH/NAD ratios and levels of β-hydroxybutyrate, was not impaired in the c.d. rats compared to the c.s. controls on diets containing 7% and 31.5% fat.
The metabolism of the erythrocyte. XIX. Factors affecting esterification of linoleate by human erythrocytes
Authors: Shastri Kamini , Rubinstein David
Published: December 2009

Factors affecting the esterification in vitro of linoleate-1-14C by intact human erythrocytes were investigated. Lecithin contained the highest proportion of the esterified fatty acid, but it was not possible to detect any incorporation into the neutral lipids. Glucose caused a slight increase in incorporation into erythrocytes which had been stored for 18 h at 4°, but had little effect on fresh cells. Esterification was proportional to the intracellular nucleotide labile phosphate level (corresponding to the ATP and ADP levels), provided the latter was less than that found in fresh erythrocytes. However, no further increase in esterification occurred when the level of nucleotide labile phosphate was raised to twice that of fresh cells by incubation for 10 h with glucose and adenine. Water-immiscible phthalate esters, used for the separation of young and old erythrocytes, increased esterification two- to three-fold without altering either its correlation with the intracellular nucleotide labile phosphate level or the distribution of the linoleate-1-14C among the various phospholipids. The oldest 5% of the cell population, whether separated by phthalate esters or in Ringer solution, showed a diminished level of nucleotide labile phosphate and a decreased rate of esterification. The presence of glucose restored the level of linoleate-1-14C incorporation by old cells to that of the remainder of the cell population. Lysolecithin increased the rate of esterification without altering the distribution of the linoleate-14C among the phospholipids, and removed the difference between normal and energy-poor cells. These data suggest that the rate-limiting step in esterification may involve an energy-sensitive transport of free fatty acids into an intracellular precursor pool rather than the fatty acid esterification (thiokinase) reaction.
The stereospecificity of subtilisin BPN′ towards 1-keto-3-carbomethoxy-1,2,3,4-tetrahydroisoquinoline
Authors: Dugas Hermann
Published: December 2009

Like α-chymotrypsin, subtilisin BPN′ reverses its normal stereospecificity when 1-keto-3-carbomethoxy-1,2,3,4-tetrahydroisoquinoline is the substrate; the D-isomer is hydrolyzed readily, the L-isomer is not. However, the enzyme retains its normal stereospecificity when the related open-chain ester N-benzoyl-alanine methyl ester is the substrate; the kinetic constants for hydrolysis of the L-isomer are comparable to those for hydrolysis of other neutral amino acid esters. These results suggest that the stereochemical requirements at the active site of subtilisin BPN′ are similar to those of α-chymotrypsin.
Influence of carcinogens and group-specific compounds on DNAse II
Authors: Melzer Marvin S.
Published: December 2009

A number of cancer-causing and group-specific compounds were tested for their effects on the activity of DNAse II. The following were almost completely inhibitory: iodoacetic acid, N-bromosuccinimide (at an N-bromosuccinimide/enzyme level ≥ 24), and H2O2 (at an H2O2/enzyme level > 10 000). Either noninhibitory or less than 30% inhibitory were iodoacetamide and diisopropylfluorophosphate. Noninhibitory were such carcinogens as beta-butyrolactone, diepoxybutane, 3-hydroxyxanthine, and ascaridole. Also noninhibitory was malonaldehyde.From these results (and others in the literature), it was concluded that (1) the carcinogens tested (at least in their unmetabolized forms) might not act directly on DNAse II in the critical reaction of the carcinogenic process, and (2) tryptophan, methionine, and/or histidine residues play important roles in the enzyme activity.
The effect of hyperoxia and hypoxia on free and bound γ-aminobutyric acid in mammalian brain
Authors: Wood J. D. , Watson W. J.
Published: December 2009

In rats and guinea pigs exposed to hyperoxic conditions, the levels of both bound and free γ-aminobutyric acid in the brain were decreased, and under hypoxic conditions both were increased. A small but significant change in the proportion of γ-aminobutyric acid in the bound form was observed in the exposed animals. The significance of the findings is discussed.
Quinone epoxides. V.1 The biosynthesis of terreic acid
Authors: Read G. , Westlake D. W. S. , Vining L. C.
Published: December 2009

Tracer studies using the 14C-labeled salts of acetic acid, 6-methylsalicylic acid, and orsellinic acid demonstrate that the carbon skeleton of terreic acid (3,4-epoxy-6-hydroxy-2,5-toluquinone), a metabolite of Aspergillus terreus, is biosynthesized by the acetate–malonate pathway and that 6-methylsalicylic acid is an intermediate in this process. Orsellinic acid does not appear to be involved. Molecular 18O is incorporated into the metabolite, and distinction can be made between incorporation at the epoxide oxygen and the three remaining oxygens on the basis of exchange rates. By this method the epoxide oxygen is shown to originate from atmospheric oxygen. The overall biosynthetic pathway is discussed.
Metabolism of 3H-11-deoxycorticosterone and 4-14C-11β-hydroxyprogesterone by rat adrenal preparations
Authors: Tsang C. P. W. , Stachenko J.
Published: December 2009

When equimoles of 4-14C-11β-hydroxyprogesterone and 1,2-3H-11-deoxycorticosterone are incubated with rat adrenal quarters for 3 h, they are incorporated to the same extent into corticosterone or aldosterone. The addition of an NADPH-generating system increases the incorporation of 3H-11-deoxycorticosterone by twofold, and that of 11β-hydroxyprogesterone by 1.6-fold. In a dilute homogenate supplemented with NADPH, only 3H-11-deoxycorticosterone was utilized as precursor of these steroids. These studies demonstrate the capacity of rat adrenal sections to hydroxylate 11β-hydroxyprogesterone to corticosterone. The fact that a dilute homogenate does not utilize 11β-hydroxyprogesterone is related to the inhibition or inactivation of 21-hydroxylase activity.
Metabolism of phosphoglycerides in E. coli IV. The positional specificity and properties of phospbolipase A
Authors: Proulx P. , Fung C. K.
Published: December 2009

The hydrolysis of labelled phosphatidylethanolamine by E. coli was studied in vitro. Phospholipase A, as detected by 32P-labelled lysophosphatidylethanolamine formation, had two pH optima, 5 and 8.4. On the other hand lysophosphofipase was active only in the alkaline range, had a pH optimum of 10, and was inhibited by high concentrations of either sodium deoxycholate or sodium lauryl sulfate. Phospholipase A required Ca2+ addition for maximal activity at both pH optima. Mg2+ also stimulated the activity but other divalent cations tested were slightly inhibitory or without effect. Sodium lauryl sulfate completely inhibited at pH 5. Experiments with singly and doubly labelled phosphatidylethanolamine indicated that phospholipase A1 activity was predominant at both acid and alkaline pH. Lower levels of phospholipase A2 were detectable only at alkaline pH.
In vitro protein synthesis directed by R17 viral ribonucleic acid. II. On the fate of mRNA in the cell-free system
Authors: Igarashi Satomi J.
Published: December 2009

In the crude E. coli B cell-free system, mRNA was hydrolyzed by contaminating nuclease activities before significant polymerization of amino acids took place. Ribosomes appeared to be one of the sources of nuclease. A modified high-salt washing procedure was developed to remove nuclease from ribosomes. RNase-free ribosomes thus obtained appeared to be inactive in poly-U-directed phenylalanine incorporation, unless poly-U binding factor was added to the system. R17 RNA could not direct amino acid incorporation in the presence of RNase-free ribosomes because binding of intact R17 RNA to ribosomes did not take place even in the presence of poly-U binding factor.
Long-chain esters in clover wax
Authors: Emery A. E. , Gear J. R.
Published: December 2009

Chemical and spectral evidence indicates that a solid waxy material, isolated from the leaves and stems of Melilotus alba (sweet clover), is a mixture of aliphatic esters. Vapor-phase chromatography of the saponified esters has shown that this fraction consists of esters of long-chain, saturated acids and alcohols containing even numbers of carbon atoms. The acids vary in length from 16 to 30 carbon atoms. The predominant alcohol contains 26 carbon atoms, but significant amounts of alcohols of 24 and 28 carbon atoms are also present.
Respiration and oxidative phosphorylation by mitochondria of red and white skeletal muscle
Authors: Rigault M. Yolanda Alvarado , Blanchaer M. C.
Published: December 2009

Mitochondria from red and white skeletal muscle of the rabbit were compared polarographically with pyruvate–malate, α-glycerophosphate, and NADH as substrates. With pyruvate–malate, the organelles from the two muscle types did not differ in O2 uptake rate ([Formula: see text] mitochondrial protein per minute at 28°) or in ADP/O ratios [Formula: see text]. However, the respiratory control ratios (r.c.r.) were significantly higher in white than in red muscle mitochondria: 5.5 ± 0.3 versus 4.4 ± 0.2 (mean ± s.e.), respectively. The respiration of the white muscle mitochondria with α-glycerophosphate was similar to that with pyruvate–malate and exhibited ADP/O and r.c.r. values of 1.5 ± 0.1 and 3.0 ± 0.1, respectively. The corresponding values for red muscle mitochondria were all lower with this substrate. The organelles from both tissues were uncoupled with NADH as substrate and yielded O2 rates of less than 5% of those with pyruvate–malate.Assuming that the in vivo permeability characteristics of the organelles resemble those described above, it can be calculated that direct penetration of glycolytically generated NADH into the mitochondria would probably be too slow for its reoxidation to occur in either muscle type at a rate compatible with aerobic carbohydrate utilization. However, the intramitochondrial portion of the α-glycerophosphate shuttle has the capacity to transport reducing equivalents to the respiratory chain at the required rate. It is as yet uncertain whether it shares this role with a malate–oxaloacetate shuttle.
Phosphate content of goose erythrocyte histones
Authors: Adams G. H. M. , Vidali G. , Neelin J. M.
Published: December 2009

Although chromatographic profiles and amino acid compositions of erythrocyte histones from normal and regenerating goose blood did not differ, characteristic fractions from regenerating blood contained more alkali-labile phosphate than did their counterparts from normal blood. Furthermore, the phosphate content of the erythrocyte-specific component was appreciably greater than that of any other histone.The problem of distinguishing between contamination and valid histone phosphate is considered; complex formation between nuclear phosphoprotein and specific histone fractions could not be unequivocally eliminated. The pronounced phosphate levels in the erythrocyte-specific histone V are discussed in relation to the prospective roles of histone phosphorylation.
Temperature-sensitive mutation. V. Infection of ts-mutant of RNA phage R17 and host cell metabolism
Authors: Igarashi S. J. , Elliott J. F. , Bissonnette R. P.
Published: December 2009

A temperature-sensitive mutant of RNA bacteriophage R17, ts24, which contains a ts-mutation in the RNA-replicating function, was used to analyze the effects of RNA phage infection on host E. coli cell metabolism in the presence and absence of phage RNA synthesis. The principal conclusions from these studies are as follows. (1) Host ribosomal RNA synthesis is inhibited by infection with R17 whether or not phage-specific RNA synthesis takes place. (2) Immediately following infection, overall protein synthesis is reduced to 10–20% of the level of synthesis occurring in noninfected cultures. (3) Phage RNA remains intact in the host cell for at least 90 min after infection. Based on these observations, a mechanism for the specific inhibition of ribosomal RNA by R17 infection was discussed.
Utilization of glycerophosphate for phospholipid synthesis by cells of Halobacterium cutirubrum
Authors: Wassef M. K. , Kates M. , Kushner D. J.
Published: December 2009

Studies on the metabolism of 14C- and 32P-glycerophosphate by whole cells and cell-free enzyme preparations showed that α-glycerophosphate is not taken up by intact H. cutirubrum cells but is first hydrolyzed to glycerol and inorganic phosphate by an active glycerophosphatase associated with the cell envelope. The glycerol and inorganic phosphate components then pass into the cells independently and are incorporated into α-glycerophosphate and phospholipids.
Stereospecificity of the glycerol kinase and the glycerophosphate dehydrogenase in Halobacterium cutirubrum
Authors: Wassef M. K. , Sarner J. , Kates M.
Published: December 2009

Glycerol kinase and glycerophosphate dehydrogenase activities have been demonstrated in the obligate halophile Halobacterium cutirubrum. Both enzymes are stereospecific for the formation of only the sn-3-glycerophosphate, and are associated with the cell envelope and cytoplasmic fractions. The stereospecificity of these enzymes in the obligate halophile is thus the same as in nonhalophiles and in higher organisms. The bearing of these findings on the biosynthetic pathway for the di-O-phytanyl glycerol ether phospholipids in H. cutirubrum is discussed.
Properties of an NADP+-specific isocitric dehydrogenase from Thiobacillus novellus
Authors: Charles A. Michael
Published: December 2009

Isocitric dehydrogenase from Thiobacillus novellus has been purified 12-fold and some of its properties were studied. The enzyme is NADP+-specific and shows an absolute requirement for a divalent cation. Mn2+ was the most effective of those tested but was replaceable to varying degrees by any of several other divalent cations. The order of effectiveness at a concentration of 3.3 × 10−5 M was Mn2+ > Co2+ > Zn2+ > Mg2+ > Ni2+ > Hg2+ > Pb2+ > Ca2+. The optimal pH was about 8.0 with both potassium phosphate and Tris–HCl buffers. Arsenate and phosphate were capable of increasing enzyme activity in the presence of low concentrations of buffer. Added phosphate resulted in maximal activity at a concentration of 40 mM. Double reciprocal plots of velocity against Pi concentration gave a [Formula: see text] of 0.38 mM. The reaction was not reversible under any of the conditions of the investigation, nor was activity enhanced by AMP. In fact, depending upon the concentration used, most of the nucleotides tested were inhibitory. The order of effectiveness was mononucleotide < dinucleotide < trinucleotide. Of interest is the observation that the enzyme was inhibited by low concentrations of oxalacetate and a concerted effect was demonstrated by glyoxylate and oxalacetate.
Factors affecting protein synthesis in rat kidney ribosome preparations
Authors: Nicholls D. M. , Ryan M. P. , Miall S. H. , Cappon I. D.
Published: December 2009

Kidney ribosomes that were prepared from the postmitochondrial supernatant or the microsomal pellet of homogenates by deoxycholate treatment consisted mainly of monomers and dimers rather than polysomes. The addition of liver postmicrosomal supernatant to kidney homogenates or to kidney microsomes did not increase the polysome yield or the incorporation of 14C-leucine into hot acid-insoluble protein. In contrast to kidney, liver ribosomes that were prepared in the presence of liver supernatant (containing ribonuclease inhibitor) had an increased proportion of polysomes and an increased incorporation of 14C-leucine into protein compared to liver ribosomes prepared in the absence of supernatant.The incorporation of 14C-leucine into protein in kidney ribosome preparations was considerably lower than it was in liver ribosome preparations. The incorporation depended on the concentration of Mg2+, GTP, and pH 5 enzymes. Following preincubation of kidney ribosomes to eliminate endogenous mRNA, the incorporation of 14C-phenylalanine into peptide using either phenylalanine or phenylalanyl-tRNA was found to depend on the addition of poly U.Ribonuclease activity in kidney supernatant and pH 5 enzyme preparations was much greater than it was in liver preparations, and may partly account for the lower polysome yield and protein synthesis in kidney.
Biosynthesis of 1,2-3H and 4-14C steroid sulfates of high specific activity
Authors: Torday J. , Hall G. , Schweitzer M. , Giroud C. J. P.
Published: December 2009

A supernatant fraction of rat liver homogenate enriched with ATP was used for the biosynthesis of the ester sulfates of several 3H and 14C steroids of the pregn-4-ene series. The method provides a simple means to prepare steroid sulfates of high specific activity for use in either metabolic studies or as reference compounds in the quantification of such conjugates by isotope assays.
Regulation of hepatic copper in the rat by the adrenal gland
Authors: Gregoriadis G. , Sourkes T. L.
Published: December 2009

The concentration of hepatic copper in the adult rat is increased above control values (17%, P < 0.05) 6 weeks following adrenalectomy. At the same time, renal copper is decreased (23%, P < 0.01) and ceruloplasmin (serum oxidase activity) is increased. Administration of deoxycorticosterone or hydrocortisone for 1–2 weeks does not affect the concentration of hepatic copper or serum ceruloplasmin in the intact rat. A role of the adrenals in the metabolism of copper is observed in animals in positive copper balance, achieved by administering Cu2+ intraperitoneally; greater amounts of copper accumulate in the liver of adrenalectomized rats than sham-operated animals. Furthermore, the rate of elimination of the excess copper from the liver of copper-injected rats is reduced following adrenalectomy. 11-Hydroxycorticosteroids have a limited but favorable effect on this process; deoxycorticosterone treatment results in higher concentrations of hepatic copper in such animals.
A uronic acid isomerase in Flavobacterium heparinum
Authors: Karapally James C. , Dietrich Carl P.
Published: December 2009

The isolation and characterization of a uronic acid isomerase from F. heparinum is described. The enzyme converts glucuronic acid and galacturonic acid to fructuronic acid and tagaturonic acid. The equilibrium point of the reaction is affected by buffers. In the presence of borate, 75% of glucuronic acid is converted to fructuronic acid. In the presence of phosphate, the equilibrium is reached when 31% of glucuronic acid is converted to fructuronic acid. Conversely, fructuronic acid and tagaturonic acid are converted to glucuronic acid and galacturonic acid, respectively. Monosaccharides derived from heparin and chondroitin sulfates do not affect the activity of the isomerase, in contrast to the monosaccharides from hyaluronic acid which have marked inhibitory (or diluting) activity upon the enzyme. The role of this enzyme in the metabolism of mucopolysaccharides is discussed.
The resemblance of the combination of human haptoglobin and double hemoglobin molecules to an antigen–antibody reaction
Authors: Malchy B. , Dixon G. H.
Published: December 2009

Human haptoglobin (Hp) combines with hemoglobin double molecules (Hb∙Hb) isolated from an inbred strain of mice, DBA/2J. When low ionic strength solutions of the two proteins are mixed, precipitates form. The extent of precipitation is dependent upon the ratios of the two proteins in a manner similar to that seen in a classical antigen–antibody precipitin reaction. In a more alkaline buffer of higher ionic strength, complexes form which remain soluble and may be resolved as a series of bands by acrylamide disc electrophoresis. The relative concentration of each band within the series depends upon the input ratios of Hp and Hb∙Hb. These results indicate that human haptoglobin is bivalent and combines with hemoglobin in a fashion analogous to the combination of an antibody with an antigen.
Synthesis of glyceryl ethers by microsomal enzymes derived from fibroblasts (L–M cells) grown in suspension cultures
Authors: Snyder Fred , Malone Boyd , Cumming Robert B.
Published: December 2009

Modified fibroblasts (L–M cells), grown in suspension cultures, contain a microsomal enzyme system that can synthesize alkyl ether bonds from long-chain fatty alcohols and glyceraldehyde 3-phosphate or dihydroxyacetone phosphate. Essential cofactors for the formation of alkyl ether bonds are ATP, CoA, and Mg2+.
Biogenetic mechanisms. I. Incorporation of 4-14C-progesterone into gitoxigenin by Digitalis purpurea
Authors: Tan Liat
Published: December 2009

In vivo administration of 4-14C-progesterone to a 6-month-old Digitalis purpurea species over a period of 4 weeks resulted in 0.477% incorporation of the radioactivity into gitoxigenin. The identity of the crystalline cardenolide isolated was established by thin-layer and gas chromatography, infrared spectroscopy, as well as isotope dilution with authentic carrier material and crystallization to constant specific activity. The role which progesterone may play as an active precursor in the biogenesis of steroid cardenolides is discussed.
Incorporation of carbon atoms from glucose into free amino acids in brain under normal and altered conditions
Authors: Yoshino Y. , Elliott K. A. C.
Published: December 2009

The time course of entry of radioactive carbon from intravenously administered [U-14C]-glucose into free amino acids in the brains of rats has been studied using an automatic amino acid analyzer coupled through a flow cell with a scintillation counter. Radioactivity appeared rapidly in alanine, aspartic acid, glutamic acid, glutamine, and γ-aminobutyric acid as previously shown, and in an unknown ninhydrin-positive substance present in very small amount. Urea, serine, and glycine became slightly radioactive. Four hours after giving the radioactive glucose, the specific activity in all soluble substances was low. In pentobarbital anesthesia, specific radioactivity was increased in alanine and decreased in γ-aminobutyric acid, aspartic and glutamic acids, and glutamine. A high proportion of radioactivity remained in glucose. Under hypoxia, alanine increased in amount but decreased in specific activity, and the specific activities of the other strongly labelled amino acids decreased. The proportion of the total radioactivity found in glucose and lactate increased. During picrotoxin and pentylenetetrazol convulsions, changes occurred which were similar to those under hypoxia. After aminooxyacetic acid administration, the well-known great increase in γ-aminobutyric acid level was found to be accompanied by a decrease in glutamate and also in aspartic acid and alanine, indicating inhibition of the three transaminases concerned. The previously observed brief rapid postmortem increase in the amount of γ-aminobutyric acid was confirmed; alanine also increased briefly but no other amino acid did so. The increased γ-aminobutyric acid had the same specific radioactivity as the original but the extra alanine was less radioactive than the original. When the γ-aminobutyric acid level had been increased by administration of aminooxyacetic acid, the rapid postmortem increase did not occur.
The kinetics of the reaction of N,N-dimethyl-2-phenylaziridinium ion with bovine erythrocyte acetylcholinesterase
Authors: Purdie Jocelyn E. , Heggie R. M.
Published: December 2009

The kinetics of the hydrolysis of N,N-dimethyl-2-phenylaziridinium ion (DPA) have been studied over the pH range 5.5–8.0 as have the kinetics of the interaction of DPA with bovine erythrocyte acetyl-cholinesterase. The enzyme is initially inhibited reversibly and subsequently irreversibly towards acetylcholine hydrolysis. The hydrolysis of DPA was found to be pH independent over the range studied while the reversible noncompetitive inhibition increased with increasing pH, the data suggesting the requirement for a basic group on the enzyme with a pKa of about 6.5.Between pH values of 6.0 and 8.0 the kinetics of the irreversible inhibition are consistent with either of two kinetically indistinguishable mechanisms, one involving transformation of the initial reversible complex and the other an independent attack on the uncomplexed enzyme. The first mechanism gives rise to a first-order rate constant which is comparable with that for the hydrolysis of DPA but which increases with decreasing pH; an acidic group on the enzyme with pKa between 6.0 and 7.0 may be involved. The second-order rate constant arising from the second treatment goes through a maximum at pH 7.3. At pH 5.5 the kinetics are not consistent with either mechanism.
Carnitine palmitoyltransferase activity and fatty acid oxidation by livers from fetal and neonatal rats
Authors: Augenfeld John , Fritz Irving B.
Published: December 2009

In liver preparations from fetal rats, the rate of palmitate oxidation to CO2 was approximately one-tenth that found in adult liver homogenates, and the rate of incorporation of labeled palmitate into acetoacetate by livers from fetal animals was approximately one-hundredth of the corresponding rate in liver preparations from neonatal rats. Shortly after birth, the hepatic rate of oxidation of long-chain fatty acids increased greatly, and in liver preparations from 2-day-old rats, the rate was faster than that observed in adult liver preparations.The changes in activity of carnitine palmitoyltransferase in hepatic mitochondria from fetal and neonatal rats were nearly parallel to changes in fatty acid oxidation. Activities in fetal liver preparations were approximately one-tenth those observed in liver mitochondria from adults, while activities in hepatic mitochondria from 2- or 3-day-old rats were slightly greater than those found in adult liver.It was concluded that the rate of hepatic fatty acid oxidation in fetal and neonatal rats, as well as in adult animals, is influenced by the levels of carnitine palmitoyltransferase activity. The possible regulatory role of carnitine and the carnitine palmitoyltransferase reaction in fatty acid oxidation is discussed.
A sensitive assay for the hemoglobin content of young developing chick blastodiscs
Authors: Wainwright S. D.
Published: December 2009

A method for assay of hemoglobin based on the peroxidase activity of the heme group was developed. The assay was sensitive to 1 × 10−2 to 2 × 10−2 μg of hemoglobin and gave a linear relationship between intensity of color developed and quantity of hemoglobin in the range 0–5 μg.With young blastodiscs of the stages of development of interest incubated on selected experimental media, the method was essentially absolutely specific for hemoglobin.
Physical and chemical studies of Mengo virus variants. III. Absorbance–temperature profiles, sedimentation in dextran sulphate gradients, and total/infectious particle ratios
Authors: Scraba D. G. , Hostvedt P. , Colter J. S.
Published: December 2009

The L, M, and S plaque-type variants of Mengo virus have been found to exhibit distinctive absorbance–temperature profiles, the temperatures at the midpoint of the hyperchromic change being 66, 60, and 65 °C, respectively. A comparison of the absorbance–temperature behaviors of whole virus and phenol-extracted viral RNA indicates that the latter has a highly compact conformation within the virus particle. L-Mengo was shown to differ markedly from the other two variants with respect to (a) rate of sedimentation in dextran sulfate density gradients, and (b) total/infectious particle ratio. A correlation of these physical properties with some of the biological properties of the Mengo variants is presented.
Biotin and glucose metabolism
Authors: Dakshinamurti K. , Tarrago-Litvak L. , Hong Ho Chong
Published: December 2009

Biotin enhances liver glucokinase in the diabetic rat. Experiments using inhibitors of protein and RNA synthesis suggest that this is mediated through de novo protein synthesis. Biotin treatment also increases the activities of other key glycolytic kinases, phosphofructokinase and pyruvate kinase, but has no effect on a bifunctional enzyme like phosphohexose isomerase.
Tumor cell metabolism in vitro: a study of incubation media
Authors: Caldwell I. C. , Chan Marianne F.
Published: December 2009

A number of incubation media which have been used in studies of the metabolism of Ehrlich ascites carcinoma (EAC) cells in vitro have been examined with respect to their abilities to support the incorporation of radioactive precursors into nucleotides and nucleic acids, and to maintain the structural integrity and tumor-inducing abilities of EAC cells. Cells incubated in the chemically-defined "Fischer's medium for leukemic cells of mice" were able to produce lethal tumors in mice after more than 16 h of incubation, maintained their structural integrity on prolonged incubation, and catalyzed high rates of incorporation of exogenously added substrates into nucleotides, RNA, and DNA. However, cells incubated in balanced salts solutions supplemented with glucose had these characteristics: (a) were unable to produce lethal tumors after 4 h of incubation, (b) released large amounts of nucleotide, nucleic acid, and protein material into the medium after less than 2 h of incubation, and (c) catalyzed the incorporation of radioactive precursors into nucleotides and RNA at much lower rates than did cells incubated in Fischer's medium, and were virtually unable to catalyze the incorporation of adenine-14C into DNA.
Enhancement of the lipolytic activity of skeletal muscle in certain physiological states
Authors: Wallach Donald P.
Published: December 2009

Four lipolytic enzyme preparations, whose existence was previously demonstrated in rat skeletal muscle, have been shown to be present in preparations from skeletal muscles of the golden hamster, the 13-lined ground squirrel, and three strains of mice. When compared with appropriate controls, statistically significant increases in specific activity of all four lipase preparations were observed in hibernating hamsters and muscular dystrophic mice. In obese hyperglycemic mice, three monoglyceride lipases were significantly increased; there was no significant increase, however, in tricaproin lipase. In hibernating 13-lined ground squirrels and aurothioglucose-treated hyperphagic mice, only the monopalmitin lipase was significantly increased.
Mechanisms of inhibition of adenine phosphoribosyltransferase by adenine nucleosides and nucleotides
Authors: Henderson J. Frank , Gadd R. E. A. , Palser H. M. , Hori M.
Published: December 2009

Kinetic studies of the inhibition of adenine phosphoribosyltransferase by adenine 6′-deoxyallofuranoside and 2′-deoxyadenylate indicate that both compounds bind to free enzyme and to the enzyme–phosphoribosylpyrophosphate complex, although they bind with different relative affinities to each enzyme form. The sites to which these inhibitors bind appear to be different from those to which substrates and products bind. Kinetic and physical studies show that adenosine diphosphate and adenosine triphosphate also bind to several enzyme forms, and that their mechanisms of inhibition of this enzyme are complex.
Phospholipid metabolism in the molluscs. II. Activities of choline kinase, ethanolamine kinase, and CTP:phosphorylethanolamine cytidyltransferase in the mollusc Helix lactea
Authors: Liang Chi-Rong , Segura M. , Strickland K. P.
Published: December 2009

The distribution of phospholipids in the mollusc Helix lactea was investigated. The results showed that ethanolamine and choline phosphoglycerides are the major phospholipids in this species, amounting to 49% and 26% of the total lipid phosphorus. The amount of ceramide 2-aminoethylphosphonate was 9% of the total phospholipids and this compound was the only phosphonolipid detected in this species. Ethanolamine and choline kinase activities were shown to be present in the high-speed supernatant fraction of snail digestive gland. The maximum activity of choline kinase was found to be higher than that of ethanolamine kinase in the same enzyme preparation. The enzyme CTP:phosphorylethanolamine cytidyltransferase was also demonstrated in the high-speed supernatant fraction of snail digestive gland. The enzymic reaction product was identified as CDP-ethanolamine by paper chromatography and radioautography. The enzymes phosphorylcholine cytidyltransferase and aminoethylphosphonate cytidyltransferase were not detected under the conditions employed in the phosphorylethanolamine cytidyltransferase assays.
Biochemistry of polyglycerophosphatides in central nervous tissue. I. On the biosynthesis, structure, and enzymatic degradation of phosphatidylglycerophosphate and phosphatidylglycerol in isolated sheep brain mitochondria
Authors: Davidson J. B. , Stanacev N. Z.
Published: December 2009

The formation of labelled phosphatidylglycerophosphate and phosphatidylglycerol from L-glycero-3-phosphate-2-3H and cytidine diphosphate (CDP)-D-diglyceride in subcellular particles of sheep brain has been studied, establishing the predominant location of this enzyme system in mitochondria. The general characteristics and the optimal conditions for the biosynthesis of these lipids have been determined and the chromatographic separation and isolation of phosphatidylglycerophosphate and phosphatidylglycerol are described. In addition, the chemical and enzymatic degradations supporting the structure and configuration for each biosynthesized lipid are presented. The enzymatic dephosphorylation of phosphatiadylglycerophosphate to phosphatidylglycerol with mitochondria isolated from sheep brain has been found. No biosynthesized cardiolipin was, however, detected.The mechanism of the enzymatic reactions for the formation of these lipids has been studied by using L-glycero-3-phosphate[33P]-2-3H and CDP-D-diglyceride; the pathway found by Kennedy et al. (1) for the biosynthesis of phosphatidylglycerol in liver is applicable in the biosynthesis of this compound in sheep brain mitochondria.
A comparison of properties of the α-lytic protease of Sorangium sp. and porcine elastase
Authors: Kaplan H. , Symonds V. B. , Dugas H. , Whitaker D. R.
Published: December 2009

The comparison is between a pancreatic and a bacterial serine protease with similar specificities, similar sequences around their catalytically functional serine and histidine residues, and with certain notable similarities in amino acid composition.The two enzymes match one another in the following respects, (a) kc depends on an ionization with a pKa of approximately 6.7 in H2O and 7.2 in 2H2O; kc/Km is reduced by 50% when H2O is replaced by 2H2O; the data are consistent with general basic catalysis by a single, unprotonated histidine residue. (b) Km is independent of pH from pH 5 to 10.5; optical rotation is independent of pH over the same range. (c) Neither enzyme is inhibited by the chloromethyl ketones derived from N-tosylglycine and N-tosyl-L-valine or by the bromomethyl ketone derived from N-tosyl-L-valine.Both enzymes have elastolytic activity and both have lytic activity towards Arthrobacter globiformis cells, but elastase has the higher elastolytic activity and the α-enzyme the higher bacteriolytic activity. The α-enzyme is more thermostable at pH 8.0.A systematic comparison was made of their esterase activities as influenced by the side chains, the N-acyl substituents, and the alcoholic groups of amino acid esters. Esters of L-alanine were the best substrates for both enzymes; esters of L-valine were moderately good substrates for the α-enzyme but not for elastase; esters of glycine, L-leucine and L-isoleucine, and D-alanine were very poor substrates for both enzymes. Both enzymes are very sensitive to the nature of the N-acyl substituent and show appreciable differences in their response to various substitutions. The alcoholic group is a less critical determinant of activity but the values of kc are not independent of the nature of the group.A reaction mechanism is proposed in which the formation of an acyl intermediate is not obligatory but is a limiting case of a general mechanism.
Indoles and auxins. X. 2,4-Dinitrophenylsulfenyl chloride, a reagent for separation and identification of naturally occurring indoles
Authors: Raj R. K. , Hutzinger O.
Published: December 2009

3-Substituted indoles react with 2,4-dinitrophenylsulfenyl chloride to give 2-(2′,4′-dinitrophenylthio)-3-indolyl derivatives. Compounds of this type were prepared from 13 naturally occurring indoles and it was shown that these derivatives are useful, in many cases, as an aid in the isolation, chromatographic separation, and identification by infrared and mass spectroscopy and melting points. The indoles can be regenerated from most derivatives by desulfuration with Raney nickel.
Myo-mositol and 2-deoxy-myo-inositol in the chrysophycean alga Monochrysis lutheri Droop
Authors: Laycock M. V. , Craigie J. S.
Published: December 2009

Chromatographic fractionation of extracts of the flagellate M. lutheri yielded 1,4/2,5-cyclohexanetetrol, 2-deoxy-myo-inositol, and myo-inositol in approximately 7%, 2%, and 0.6% of the cellular dry weight. The distribution of cyclitols in algae is summarized.
Kinetic mechanism of phosphorylase a, II. Isotope exchange studies at equilibrium
Authors: Engers H. D. , Bridger W. A. , Madsen N. B.
Published: December 2009

In order to confirm the kinetic mechanism which was proposed for rabbit muscle phosphorylase a on the basis of initial rate studies and UDP-glucose inhibition experiments, isotope exchange studies at equilibrium were performed, both in the presence and absence of the modifier AMP.Both the 14C-glucose [Formula: see text] and the [Formula: see text]1-phosphate equilibrium exchange rates increased to a maximum as the concentrations of the varied substrates became saturating, either in the presence or absence of AMP. The plateaus observed in these experiments indicate the lack of inhibition of the exchange of one pair of substrates when the concentration of the other substrate pair was raised, and confirms the proposed random addition of substrates to the enzyme.The fact that similar exchange rates were observed for either reaction direction reinforced the concept that rapid equilibrium conditions apply to the phosphorylase a mechanism; i.e. the interconversion of the ternary complexes tends to be the rate-limiting step in the reaction sequence.Maximal velocities determined from initial rate data reported in the previous paper agreed with those calculated from isotope exchange rates.
Impaired labelling of liver phosphatidylethanolamine from ethanolamine-14C in choline deficiency
Authors: Haines D. S. M. , Rose C. I.
Published: December 2009

Ethanolamine-14C was injected intraportally to eight rats after 3 days of choline-deficient (c.d.) feeding and to eight choline-supplemented (c.s.) rats. The rats were killed in groups of two after 4, 8, 18, and 32 min. Much less 14C was incorporated into phosphatidylethanolamine and phosphatidylcholine in the c.d. livers, while the level of the former phospholipid was increased and the latter was decreased in these livers.The liver water-soluble constituents were separated by anion and cation exchange chromatography and the following components were analyzed : choline, ethanolamine, glycerophosphocholine, glycerophosphoethanolamine, choline phosphate, ethanolamine phosphate, and CDP-ethanolamine. In c.d. liver the levels of ethanolamine and its derivatives were increased while choline and choline phosphate were reduced. There was a lower incorporation of ethanolamine-14C into CDP-ethanolamine in the deficient livers whereas the specific radioactivities of ethanolamine and ethanolamine phosphate were increased. These findings are interpreted as indicating the existence of a block at the CTP : ethanolamine phosphate transferase step of phosphatidylethanolamine synthesis in c.d. liver.
Hemoglobin Manitoba: α102(G9) serine replaced by arginine
Authors: Crookston J. H. , Farquharson Helen A. , Kinderlerer Judith L. , Lehmann H.
Published: December 2009

In a Canadian family of British origin, a new hemoglobin variant, hemoglobin Manitoba, was observed. It was shown to differ from hemoglobin A by having a residue of arginine in place of serine in position 102 of the α-chain (helical notation G9). There was no evidence that this hemoglobin variant has any adverse clinical symptoms.
Nuclear magnetic resonance and ultraviolet studies of the effect of p2H on reduced nicotinamide–adenine dinucleotide
Authors: Griffith P. R. , Nye M. J. , Alexander J. C.
Published: December 2009

The effect of p2H on the chemical shifts of two adenine protons and one reduced nicotinamide proton of β-NADH have been examined. The adenine protons had a single pK at a p2H 3.85. The reduced nicotinamide proton showed no pK in the range p2H 3.00 to p2H 7.00. At low p2H values a new peak appeared in the nuclear magnetic resonance spectrum 0.31 p.p.m. downfield from the nicotinamide C-2 proton of β-NADH, and the nicotinamide C-2 proton peak gradually disappeared. It is suggested that this new peak is responsible for some of the anomalies in published results. The alterations in the ultraviolet spectra also indicate a change in the structure within the reduced nicotinamide moiety of β-NADH at low p2H values.