bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphonolipids. XXIV. Phosphonolipid metabolites. Synthesis of L-α-glyceryl-(N-methyl-2-aminoethyl)phosphonate
Authors: Baer Erich , Pavanaram Sripada K.
Published: December 2009

The synthesis of L-α-glyceryl-(N-methyl-2-aminoethyl)phosphonate, a possible intermediate in the biosynthesis and metabolism of L-α-phosphono(N-methyl)cephalins, is described. It was obtained by phosphonylating D-acetone glycerol with (N-carbobenzoxy,N-methyl-2-aminoethyl)phosphonic acid monochloride and triethylamine, and removing the protective isopropylidene and carbobenzoxy groups by mild acid hydrolysis and catalytic hydrogenolysis, respectively.
Incorporation de la radioactivité du chlorure de (2-chloroéthyl) triméthylammonium-1,2-14C dans la phosphatidylcholine de folioles de luzerne
Authors: Willemot C. , Belzile L.
Published: December 2009

(2-Chloroethyl)trimethylammonium chloride, a plant growth retardant, is only slowly metabolized by alfalfa leaflets. It is incorporated mainly into the choline moiety of phosphatidylcholine. Free choline-1,2-14C could not be demonstrated in these tissues after their incubation in the presence of (2-chloroethyl)-trimethylammonium chloride-1,2-14C.
Synthesis of α-phosphotidic acids
Authors: Baer Erich , Basu Hemendra
Published: December 2009

A procedure permitting the synthesis of both optical isomers as well as the racemic form of saturated or unsaturated phosphotidic acids is reported. The phosphotidic acids are obtainable by treating the pyridinium salts of L-, D-, or DL-dihydroxypropylphosphonic acid for 24 h at 80° with a mixture of the anhydride and the tetraethylammonium salt of the fatty acid to be introduced, and separating the reaction products by column chromatography on silicic acid. The preparation of the dipalmitoyl and distearoyl L-dihydroxypropylphosphonic acids is described.
Biosynthèse des glycoprotéines. XIV. Role des sites cytoplasmiques dans les cellules embryonnaires et néoplasiques en culture en suspension
Authors: Louisot Pierre , Lebre Danièle , Pradal Marie-Bénédicte , Gresle Jeanine , Got René
Published: December 2009

In embryonic and neoplastic cells suspended in culture medium, incorporation of labelled glucosamine into glycoprotein occurred in three distinct subcellular sites: endoplasmic membranes, ribosomes, and cell sap, of which the first was quantitatively the most important. The presence of labelled glucosamine on polysomes indicates that the carbohydrate moiety starts to become attached to the polypeptide while the glycoprotein is still linked to the polysome.
The characterization of the 12 S "globulin" from rapeseed and its glycoprotein component
Authors: Goding L. A. , Bhatty R. S. , Finlayson A. J.
Published: December 2009

A 12 S globulin was isolated from each of the two species of rapeseed (B. napus L. and B. campestris L.) and they have been shown to be similar in terms of amino acid composition, amino terminal amino acids, number of subfractions, and carbohydrate content. One of the major proteins, a glycoprotein, present in each of the 12 S aggregates, was isolated and purified. Its amino acid composition, carbohydrate content, N-terminal amino acids, and sedimentation coefficient are reported herein.
Amide groups of some tryptic peptides from the β-chain of horse hemoglobin
Authors: Smith David B. , Chung W. P.
Published: December 2009

Amide groups of the 'soluble' tryptic peptides (residues 1–82 and 117–146) of the β-chain of horse hemoglobin are: position 2, Gln; 19, Asn; 39, Gln; 50, Asn; 57, Asn; 80, Asn; 127, Gln; 131, Gln; 139, Asn.The heretofore undetermined sequence involving residues 52–54 is Gly∙Ala∙Val.The identifications of residues 20, 43, and 72 have been confirmed as Glu, Asp, and Gly.
Protein-bound amide groups in brain
Authors: Yoshino Y. , Elliott K. A. C.
Published: December 2009

The amount of ammonia that can be liberated from protein from cerebral cortex by acid hydrolysis is significantly lower in brain from rats killed during picrotoxin-induced convulsions than from rats killed during pentobarbital narcosis. Protein from normal animals gave intermediate values. No differences were found in amounts of aspartic and glutamic acids or their amides released by hydrolysis by the protease from Streptomyces griseus. The protein-bound amides appear to turn over less rapidly than the dicarboxylic acids.
A ribosomal-bound aminopeptidase in Escherichia coli B: purification and properties
Authors: Dick A. J. , Matheson A. T. , Wang J. H.
Published: December 2009

Two procedures have been developed for the large-scale purification from Escherichia coli B of a ribosomal-bound aminopeptidase in a stable form: one involving the digestion of the ribosome with pancreatic RNase and the other the selective removal of the aminopeptidase from the ribosomal surface with NH4Cl. The enzyme, as isolated from the ribosome, is a polymeric protein composed of monomeric units with a molecular weight of approximately 60 000 Daltons. The purified enzyme is activated by β-mercaptoethanol or dithiothreitol, although at high concentrations dithiothreitol inhibits peptidase activity. Propylene glycol also inhibits the enzyme. The enzyme is stable at 70° in the presence of free SH groups.
Reaction of amino acids with guanidinating agents
Authors: Allen Lynn C. , Viswanatha T.
Published: December 2009

The reaction of amino acids with three guanidinating agents, viz. 2-methylpseudourea, 2-methyl-2-thiopseudourea, and guanyl-3,5-dimethylpyrazole, was investigated. The α-amino group of amino acids with an aliphatic side chain was readily convertible to the guanido group. However, the α-amino group of other amino acids was found to be either refractory or slow toward such modification.
Increased serum haptoglobin following exposure to a hyperbaric environment
Authors: Uddin D. E. , Sellers W. H.
Published: December 2009

Sprague–Dawley rats were exposed to a 19.2 atmospheres absolute helium environment with an oxygen partial pressure of 0.21 atmosphere for 3 h. Haptoglobin levels were measured on serum samples obtained 24 h before exposure and at intervals after decompression. Serum haptoglobin increased twofold within 24 h after decompression and remained elevated for at least 3 days.
Substrate Characteristics of Human Liver Aldehyde Dehydrogenase
Authors: Bodley F. H. , Blair A. H.
Published: December 2009

Human liver NAD+-dependent aldehyde dehydrogenase oxidizes several aldehydes which differ in the extent of their hydration in aqueous solution. Results of experiments indicate that the free carbonyl form is the operative substrate. When nonenzymatic hydration of acetaldehyde was slower than the enzymatic oxidation reaction, acetaldehyde which initially was anhydrous was completely oxidized at an almost linear rate. By contrast, oxidation of acetaldehyde already in equilibrium with hydrate was biphasic. An initial rapid reaction accounted for approximately half the total aldehyde, i.e. the free aldehyde. During the second stage the acetaldehyde, initially in hydrate form, was oxidized at a reduced rate expected for a prior rate-limiting dehydration step. Small amounts of hydroxylamine, capable of reacting rapidly with free formaldehyde, caused transient inhibition of oxidation of aqueous formaldehyde (which is almost completely hydrated). Furthermore, Michaelis constants for crotonaldehyde and benzaldehyde (which are largely unhydrated in aqueous solution) were very low.
Deoxyribonucleic Acid Polymerase from Immature Testes of Salmon
Authors: Tarr H. L. A. , Gardner Linda
Published: December 2009

A simple procedure for partial purification of a DNA polymerase from immature testes of salmon (Oncorhynchus nerka) in which 20% glycerol and 2 mM dithiothreitol are used to protect the enzyme is described. The enzyme has a specific activity of 17–45 nmoles of deoxyribonucleoside triphosphate (dTTP) incorporated into DNA per milligram protein per hour at 25 °C. It has a specific requirement for Mg2+ or Mn2+, for four deoxyribonucleoside triphosphates, and for a DNA primer. The latter is best supplied by a DNA duplex that has undergone limited digestion with pancreatic DNase or by polydeoxyadenylate polydeoxythymidylate alternating copolymer (poly d(A–T)) that has been similarly treated. Native and heat-denatured DNA are poor primers. The enzyme is strongly inhibited by pancreatic DNase and pyrophosphate, less strongly by actinomycin D, and is markedly stimulated by EDTA. Addition of KCl and NaCl causes inhibition that at 100 mM concentration is 70% with KCl and 80% with NaCl. The enzyme loses 50% of its activity in 15 min at 35 °C and in 3 h at 30 °C. At 30 °C glycerol (47%), DNA, and bovine serum albumin (2 mg/ml) retard loss in activity. With poly d(A–T) primer, incorporation of α-32P-dATP into DNA proceeds for only a short time and then ceases unless dTTP is present, when incorporation continues. When the products formed in such reactions are subjected to nearest-neighbor frequency analysis only 3′-dTMP possesses radioactivity. Polydeoxyguanylate polydeoxycytidylate linear polymer has no priming activity. The product of the DNA polymerase formed a band in a buoyant density gradient of CsCl at a density similar to that of the DNA primer.
The Isolation and Identification of Androstenediol Sulfate from Spermatic Vein Blood and Testes of the Boar
Authors: Raeside J. I. , Howells G. A.
Published: December 2009

A method is described for the extraction and purification of steroid sulfates from testicular tissues and blood of the boar. Androstenediol sulfate (3β, 17β-dihydroxy-5-androstene 3-sulfate) was isolated from extracts of both spermatic vein blood and boar testis. Final identification was achieved by infrared spectroscopy, as the ammonium salt of androstenediol 3-sulfate 17-acetate. Additional evidence of identity was obtained with the 3-monosulfate of androstenediol-7α-3H as an internal standard in several chromatographic systems for steroid sulfates, and for free steroids after hydrolysis. Androstenediol sulfate was not detected in peripheral or spermatic arterial blood, and it was concluded that androstenediol sulfate is a major secretory product of the boar testis.
Development of Rat Liver Adenylcyclase
Authors: Bar Hans-Peter , Hahn Peter
Published: December 2009

A developmental study of rat liver adenylcyclase and of its sensitivity to stimulation by adrenalin, glucagon, and NaF was carried out. During the last days of prenatal development, basal activity and hormone or NaF stimulated activity rise. Maximal levels are reached between day 2 and 10 after birth. Thereafter, adrenalin-stimulated adenylcyclase activity decreases considerably. In relation to basal activity, glucagon (and NaF) sensitivity increases with age while adrenalin sensitivity is sharply reduced after 10 days of age. These results may be related to changes in specific enzyme inducibility and/or carbohydrate metabolism known to occur in the course of development of rat liver. Additive hormonal stimulation was only observed in preparations obtained from animals which were at least 30 days of age.
The Sulfhydryl Content of Rabbit and Trout Myosins in Relation to Protein Stability
Authors: Buttkus H.
Published: December 2009

Rabbit and trout myosins, prepared under painstaking conditions to exclude all incidental heavy metal contamination from reagents, water, glassware, and other utensils, contained 42 free sulfhydryl (SH) groups per 5 × 105 g when the analysis was carried out with the Ellman reagent, 5,5′-dithiobis-2-nitrobenzoic acid, in the presence of 8 M urea which was 6 mM in ethylenediaminetetraacetic acid (EDTA). In the absence of EDTA, 40 free SH groups were determined, while performic-acid-oxidized myosin preparations yielded 42 cysteic acid (half-cystine) residues by amino acid analysis. The results indicated that no disulfide bonds were present in the native myosin molecules. The specific enzyme activity (ATPase) remained constant at a relatively high value of 1.38 to 1.45 μmoles P1 per milligram protein per minute over 4 weeks of storage at 0°. Such myosin preparations were also homogeneous in the ultracentrifuge up to 4 weeks.In myosins prepared with two times distilled water and "reagent grade" chemicals which had not been purified by passage over cation exchange resins, the SH content decreased after 1–2 days at 0°, to 37 SH per 5 × 105 g of protein, and this oxidized form of myosin showed aggregate peaks in the schlieren optical system of the ultracentrifuge after 3 days of storage at 0°.Trout myosin in the presence of traces of heavy metals was more susceptible to oxidation than rabbit myosin.
Time Course of Enzyme Adaptation. III. Periodic and Nonperiodic Responses of Rat Liver Enzyme Activities to Diets in Meal-Fed Rats
Authors: Szepesi B. , Freedland R. A.
Published: December 2009

Enzymes associated with carbohydrate and amino acid metabolism as well as other liver constituents were studied in rats meal-fed, daily for 60 min, diets consisting of corn oil, salt, and vitamins plus 75% carbohydrate and 15% casein or a 90% casein diet. Relative liver size and the levels of liver glycogen and total and soluble liver protein were subject to periodic variation after the ingestion of a meal. They reached maximums about 6–12 h after the meal and then declined. In the rats fed the 90% casein diet the onset of increases was delayed after the first meal.The activity of glucose-6-phosphatase was increased by a fructose diet and the high-protein diet, but no periodicity was observed. The activities of fructose-1, 6-diphosphatase, dihydroxyacetone kinase, and malic enzyme were not subject to periodic variation, and these enzymes were not increased by the fructose or high-protein diets. Serine dehydrase activity was increased by the high-protein diet, but the question of periodicity cannot be resolved with the available data.The tyrosine–α-ketoglutarate transaminase activity in rats fed a 75% glucose – 15% casein diet was subject to periodic variation. Maximum activity occurred just before feeding, and minimum activity 12 h after feeding. In the rats fed the 90% casein diet the activity of the enzyme was considerably increased, and was already maximum 3 h after the meal. The activity then decreased to a relatively high minimum 12 h after the meal, at which time it began to increase again.The activities of pyruvate kinase, glucose-6-phosphate dehydrogenase, and phosphohexose isomerase were all subject to periodicity in the glucose-fed rats. In the rats fed the high-protein diet, there was a periodic response in activity of both pyruvate kinase and glucose-6-phosphate dehydrogenase after the first meal; but enzyme activity remained minimum after the second meal. Glucose-6-phosphate dehydrogenase and phosphohexose isomerase activities were increased after three meals of the fructose diet, and were higher than in glucose-fed rats even 24 h after a meal. Maximum activity of these three enzymes occurred 12 h after the meal. There was only small periodicity in the activity of glutamic–pyruvic transaminase. The activity of this enzyme was increased by the high-protein diet and also by the high-fructose diet, although the latter effect was only temporary. The possible importance of certain types of adaptations in meal-fed rats was discussed in connection with physiological requirements.
The Isolation of Chymotrypsin-Like Enzymes by Affinity Chromatography Using Sepharose–4-Phenyibutyiamine
Authors: Stevenson Kenneth J. , Landman Amiram
Published: December 2009

Affinity chromatography of chymotrypsin-like proteases on a column of Sepharose–4-phenylbutylamine (PBA) has been developed. Sepharose–PBA (Sepharose–NH∙[CH2]4∙C6H5) has been shown to selectively adsorb chymotrypsin α and B from weakly alkaline solutions and to allow to pass through unretarded porcine trypsin, bovine trypsinogen, and chymotrypsin α modified with active-site-directed irreversible inhibitors. Chymotrypsinogen A and bovine trypsin were only slightly retarded whereas a preparation of subtilisin was markedly retarded and separated into two distinct peaks. Sepharose–PBA has been utilized successfully for the selective isolation of chymotryps in-like proteases from extracts of moose pancreas (Alces alces).
Tetranitromethane as a Nitrating Reagent for Tyrosine and Tyrosine-Containing Peptides and Proteins
Authors: Boyd N. D. , Smith David B.
Published: December 2009

After nitration of hemoglobin and ribonuclease with tetranitromethane, the sum of tyrosine and nitrotyrosine accounted for 80% or less of the tyrosyl residues known to be present in these proteins. Reasons for this discrepancy were explored by nitrating tyrosine, glycyltyrosine, and glycyltyrosylglycine. Ninhydrin-negative substances containing the carbon atoms of tyrosine were isolated in addition to nitrated tyrosines, which may account for the apparent loss of tyrosine in nitrated proteins.
A Gastric Inhibitory Polypeptide. I. The Amino Acid Composition and the Tryptic Peptides
Authors: Brown John C.
Published: December 2009

The partial structure of a polypeptide with inhibitory activity for gastric secretion has been found to be Tyr–(Ala2, Asx, Glx, Gly, Ile2, Phe, Ser2, Thr, Tyr)–Met–Asp–Lys–Ile–Arg–Gln–(Ala, Asx2, Glx2–3, Leu, Phe, Val, Trp)–Lys–Gly–Lys–Lys–Ser–Asp–Trp–Lys–His–(Asx, Ile, Thr, Gln).
Synthesis of 2,3-Diphosphono-DL-glyceric Acid, a Racemic Analogue of 2,3-Diphospho-D-glyceric Acid, the Cofactor of both Phosphoglyceric Acid Mutase and Hemoglobin
Authors: Baer Erich , Robinson Ranga
Published: December 2009

2,3-Diphosphono-DL-glyceric acid, a racemic phosphonic acid, analogue of 2,3-diphospho-D-glyceric acid, the cofactor of phosphoglyceric acid mutase and hemoglobin, has been synthesized. It was obtained by treating the methyl esters of either β-chlorolactic acid, β-bromolactic acid, or glyceric acid with triethyl phosphite at 140–145° for 48 h, hydrolyzing the major reaction product tetraethyl 2,3-diphosphono-DL-glyceric acid methyl ester with concentrated hydrobromic acid at 140° for 24 h, and isolating 2,3-diphosphono-DL-glyceric acid as pentabarium or tricyclohexylammonium salt. 2,3-Diphosphonoglyceric acid and 2,3-diphosphoglyceric acid are readily distinguished from each other by chromatographic and chemical as well as by spectroscopic methods.
Acid Phosphatase During Development of the Black Carpet Beetle Attagenus megatoma (Fab.)
Authors: Nath J. , Butler L.
Published: December 2009

The specific activity for free and bound fractions of acid phosphatase revealed age-dependent alterations during the development of the black carpet beetle, Attagenus megatoma (Fab.). Both fractions exhibited highest activity at the pupal stage. The specific activity appears to be related to the biology of the organism.
The Phosphorus Components of Solubilized Erythrocyte Membrane Protein
Authors: Palmer F. B. St. C. , Verpoorte J. A.
Published: December 2009

Membrane protein preparations were obtained by n-butanol extraction of salt-free aqueous suspensions of human erythrocyte ghosts. The solubilized protein contained 4.5% carbohydrate, including glucosamine and galactosamine, 1.7% sialic acid, and 0.2% phosphorus. Gel electrophoresis indicated the presence of a large number of proteins in the solubilized fraction. Of the phosphorus present 15% could be extracted with chloroform–methanol (2/1) and was shown to consist of phosphatidylserine and some phosphatidylinositol. A further 65% of the phosphorus was extracted with chloroform–methanol–HCl (200/100/1) and this extract was shown to consist principally of diphosphoinositide and triphosphoinositide. The remaining protein-bound phosphorus, representing 0.03% of the protein, could not be separated from the protein. Following treatment with the organic solvents the protein was resolubilized. The carbohydrate and sialic acid concentrations and the gel electrophoretic pattern were not altered. Following incubation of erythrocytes with inorganic 32P, the polyphosphoinositides were rapidly labelled. The phosphoprotein was also rapidly labelled but to a lesser extent. The phosphatidylinositol and phosphatidylserine were very poorly labelled.
Sex Hormone Control Mechanisms. I. Effect of Estrogen and Progesterone on Major Cellular Components in Chicken (Gallus domesticus) Oviducts
Authors: Yu John Y.-L. , Campbell L. D. , Marquardt R. R.
Published: December 2009

The role and mode of action of sex hormones in the regulation of avian oviduct metabolism have been investigated. The oviducts of chicks treated with repeated injections of various sex hormones and of untreated hens have been analyzed for their contents of DNA, RNA, protein, lipids, glucose, and glycogen.Estrogen induces a profound growth of chick oviduct primarily by hyperplasia (increased amount of DNA). Cellular hypertrophy (indicated by the ratio dry matter/DNA) accounts for a smaller proportion of the total oviduct growth. Progesterone alone seems to have little or no effect on oviduct growth. Progesterone, in combination with estrogen, however, antagonizes the estrogen-induced hyperplasia of oviduct, but synergizes with estrogen in eliciting cellular hypertrophy. The increase of oviduct growth as influenced by the hormones is mainly contributed to by relatively proportional increases of both protein and lipids. In all cases the changes in total protein parallel the changes in total RNA, thus suggesting RNA formation as a prerequisite for hormonal induction of protein synthesis. Electrophoresis of the soluble oviduct proteins shows that there are qualitative differences among the various treatment groups. Estrogen or estrogen with low level of progesterone is needed for ovalbumin formation. Estrogen or progesterone induces significant increases in glycogen concentrations; combinations of the two hormones exhibit a synergistic effect. The hormone-stimulated synthesis of glycogen seems to depend on accelerated uptake of glucose by oviduct cells.The levels of various cellular components in the hormone-treated chicks are interpreted partially in terms of data obtained from mature hens. The results are discussed in terms of hormone control mechanisms and estrogen–progesterone interactions.
Studies on Mitochondria. I. Mitochondrial DNA in Relation to Morphological Development of Sarcosomes in Thoracic Muscles of the African Desert Locust (Schistocerca gregaria Forsk)
Authors: Tanguay R. , Chaudhary K. D.
Published: December 2009

Variations in the levels of mitochondrial DNA obtained from nuclei-free mitochondria have been investigated in relation to morphological growth of these organelles in the developing thoracic muscles of Schistocerca gregaria. Optimal conditions for the estimation of muscle DNA were studied. Kinetics of DNase I treatment of the mitochondria at different temperatures have been established. Relatively high mitochondrial DNA values (ranging from 1–7 μg/mg protein) are noted in the thoracic muscle mitochondria. During mitochondrial development in the adult, a decrease in mitochondrial DNA per milligram protein is noted (4.7–1.2 μg). The significance of these findings is discussed.
Correlations between Optical Rotatory Dispersion and Other Spectroscopic Properties of Ferricytochrome c (Horse Heart)
Authors: Skov K. , Williams G. R.
Published: December 2009

One transition in the Soret region of ferricytochrome c has essentially the same pH, temperature, solvent, and conformational requirements as the 695 nm band. An important role for tyrosine in maintaining a structure with these spectral properties is indicated.
Regulation of Chloramphenicol Synthesis in Streptomyces sp. 3022a. 3-Deoxy-D-arabino-heptulosonate 7-Phosphate Synthetase
Authors: Lowe D. A. , Westlake D. W. S.
Published: December 2009

The repression and end-product inhibition of 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthetase were studied in a chloramphenicol-producing Streptomycetes. Synthesis of DAHP synthetase was repressed by p-hydroxybenzoate, and enzyme activity was inhibited competitively by sugar phosphates, especially D-ribose 5-phosphate. The presence of chloramphenicol, aromatic amino acids, or shikimic acid pathway intermediates did not repress enzyme synthesis nor inhibit enzyme activity. Chloramphenicol production by growing cultures was not affected by the intermediates or end products of the shikimic acid pathway nor by the repression of DAHP synthetase. Purification of DAHP synthetase activity indicated the presence of a single enzyme protein with a molecular weight of 88 000.
Studies on the Metabolism of Nuclear Basic Proteins After Radiation In Vitro
Authors: Ghosh Mira
Published: December 2009

Exposure of isolated rabbit lymphocytes to 1000 R γ-radiation results in an increased rate of incorporation of amino acids-14C into cellular proteins during the first hour after irradiation. Fractionation of the proteins showed that the synthesis of basic proteins extracted from the nucleus was most affected. Two factors contributed to this apparent stimulation of protein synthesis by irradiation: (a) a transient increase in the amount of amino acid-14C available for protein synthesis in the cell; and (b) an increase in concentration of sodium ions in the cell. It is suggested that much of the observed increase in amino acid incorporation after irradiation of the lymphocytes is caused by radiation-induced changes in cell permeability.
Cystathionine Synthase from Rat Liver: Partial Purification and Properties
Authors: Brown F. Christine , Gordon P. H.
Published: December 2009

Cystathionine synthase which has been purified about 1000-fold from rat liver has absorbance maxima at 280, 360, and 428 mμ. Treating the enzyme with cysteine apparently affects the removal of pyridoxal phosphate and destroys the enzyme activity. So does reduction with borohydride. However, in neither case is the spectrum affected. These observations suggest that pyridoxal phosphate may be bound to cystathionine synthase in an atypical fashion.Mercuric ions strongly inhibit the enzyme, but not in the presence of serine; hydroxylamine inhibits, but not in the presence of substrates. Other carbonyl reagents inhibit little if at all. Sulfate ions activate the enzyme.A new assay procedure for cystathionine synthase has been devised. In the presence of 5,5′-dithiobis-(2-nitrobenzoic acid), the enzyme catalyzes the degradation of cystathionine to serine and homocysteine. The rate of increase in absorbance at 412 mμ is a measure of enzyme concentration.
Interpretation of Nonhyperbolic Behavior in Enzymic Systems. I. Differentiation of Model Mechanisms
Authors: Wong J. Tze-Fei , Endrenyi Laszlo
Published: December 2009

Mechanistic interpretation of nonhyperbolic rate and binding responses of enzymic reactions involves interlaced distinctions between steady-state and quasi-equilibrium kinetics, between the effects of K, V, and KV types of subunit interactions, and between the effects of different model mechanisms. Therefore (a) the steady-state and quasi-equilibrium predictions of selected kinetic models were analyzed. In most instances the degree of the rate function is a good discriminator between the two types of kinetics. (b) Sensitive detection of K effects in quasi-equilibrium is possible by observing the dependence of the ratio (relative velocity/fractional binding) on the substrate concentration, (c) Relationships between Adair binding constants and constants of models proposed by Pauling, by Monod et al., and by Koshland et al. permit testing the validity of these models to experimental binding data. For illustration the results of Roughton on the binding of oxygen to sheep hemoglobin have been analyzed, which appear to exclude the applicability of models of Pauling and Koshland, but may admit the mechanism of Monod et al. These criteria have been discussed in terms of a general scheme of presently feasible model differentiations.
N6-(Δ2-Isopentenyl)adenosine: Its Conversion to Inosine, Catalyzed By Adenosine Aminohydrolases From Chicken Bone Marrow and Calf Intestinal Mucosa
Authors: Hall Ross H. , Alam Syed N. , McLennan B. D. , Terrine Claude , Guern Jean
Published: December 2009

N6-(Δ2-Isopentenyl)adenosine, a component of tRNA, displays biological activity in both plant and animal systems. As part of a study of the biological behavior of this nucleoside, its degradation in animal tissues has been studied. An enzyme that catalyzes conversion of this nucleoside to inosine has been partially purified from chicken bone marrow. The enzyme preparation also catalyzes conversion of adenosine to inosine at about 40 times the rate of conversion of N6-(Δ2-isopentenyl)adenosine. A series of analogues of this nucleoside has been tested as substrates. The Δ3-isomer, n-pentyl, isopentyl, and furfuryl derivatives are readily cleaved. Hydroxylated derivatives of the Δ2-isopentenyl side chain, however, do not serve as substrates. Adenosine aminohydrolase from calf intestinal mucosa also catalyzes conversion of N6-(Δ2-isopentenyl)adenosine to inosine, although in order to obtain a measurable rate, the concentration of enzyme must be about 1000 times that needed to catalyze conversion of adenosine.
The Fixation and Retention of Viral and Mammalian Deoxyribonucleic Acids on Nitrocellulose Filters
Authors: Hudson James B.
Published: December 2009

A study has been made of the factors involved in the ability of denatured deoxyribonucleic acid to bind irreversibly to three different brands of nitrocellulose filters. The DNA was obtained from Polyoma virus: from the mouse line of L-929 cells in monolayer culture, and from mouse embryos. It was found that, although smaller size DNA could be fixed well to nitrocellulose filters, considerable loss of such DNA occurred during the incubation procedures used for standard hybridization tests. In addition, loss of fixed DNA was enhanced by increasing the temperature, or decreasing the salt concentration, of the incubation medium. Thus DNA of molecular weight 3 × 106 daltons could be retained quantitatively on the filters during incubation in 0.9 M NaCl – 0.09 M sodium citrate, at a temperature of 65° for not more than 24 h. A decrease in ionic strength or an increase of temperature or time of incubation encouraged loss of DNA. The DNA of smaller molecular size was correspondingly more susceptible to loss. For DNA smaller than 3.0 × 106 mol wt, hybridization should be carried out at lower temperature in the presence of formamide.The three commonly used brands of nitrocellulose filters were equivalent in their ability to adsorb and irreversibly fix each of the DNA preparations tested, and in the capacity of the fixed DNA to hybridize with complementary RNA.
Purification and Characterization of Cytochrome 553 from the Chrysophycean Alga Monochrysis lutheri
Authors: Laycock M. V. , Craigie J. S.
Published: December 2009

Cytochrome 553, an electron carrier in photosynthesis and a functional analogue of cytochrome f of higher plants, was isolated from Monochrysis lutheri and purified by salt fractionation, chromatography, and isoelectric focussing. Absorption maxima occurred at 275, 320, 416, 523, and 553 nm in the reduced form. The α-absorption peak was symmetrical and had an extinction coefficient of 25.9 mM−1 cm−1. The molecular weight was 11 100 by equilibrium centrifugation, 12 400 from iron determinations, and 10 300 from the amino acid composition. The molecule consisted of one heme group and 91 amino acid residues including two cysteine residues and one each of histidine, arginine, tryptophan, methionine, and proline. Other physical properties measured were: the sedimentation coefficient, 1.3 S; the normal oxidation reduction potential, + 0.388 V; and the isoelectric point, pH 3.75.
Multiple Molecular Forms of Avian Aldolases. V. Purification and Molecular Properties of Chicken (Gallus domesticus) Liver Aldolase
Authors: Marquardt Ronald R.
Published: December 2009

Aldolase (fructose-1,6-diphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) was purified from chicken liver. The enzyme was shown to be homogeneous according to the following criteria: purification to a constant specific activity following sequential chromatography on carboxymethyl-Sephadex and Sephadex G-200, electrophoresis on cellulose acetate strips, sedimentation velocity analysis, absence of 10 other glycolytic enzymes, and immunodiffusion in agar.The sedimentation coefficient (s°20w 8.0), Stokes radius (47 Å), diffusion constant (D°20w 4.0 × 10−7 cm2/s), and molecular weight (160 000) are similar to those of rabbit liver aldolase and the muscle and brain enzymes from both chickens and rabbits.
The Enthalpy Change of the Hydrolysis of Adenosine Triphosphate by Rat Liver Mitochondria
Authors: Cereijo-Santaló Roberto
Published: December 2009

The enthalpy change of the hydrolysis of ATP by rat liver mitochondria was studied using a differential calorimeter. This calorimeter is capable of working as a perfect adiabatic system within the time limits and temperature gradients of our experiments. Samples can be withdrawn from the incubation medium without interference with the temperature measurements.The enthalpy of ionization of Tris was found to be −11.28 ± 0.17 kcal mole−1. The enthalpy of ATP hydrolysis in the presence of either 2,4-dinitrophenol or valinomycin was −6.2 ± 0.1 kcal mole−1.
Phospholipase A2: Comparative Action of Three Different Enzyme Preparations on Selected Lipoprotein Systems
Authors: Uthe J. F. , Magee W. L.
Published: December 2009

The actions of phospholipase A2 preparations from a snake venom (Crotalus adamanteus) and from beef and human pancreas on selected lipoproteins have been compared. The mammalian enzymes were inhibited by Na+ and K+ ions, an effect which may be explained by their relatively high isoelectric points. The venom enzyme exhibited a higher specific activity when acting on beef serum than was observed with any of the other substrates tested. The pancreatic enzymes did not hydrolyze beef serum phospholipids. None of the enzyme preparations was capable of attacking intact beef erythrocytes. The results indicate that different phospholipases are highly specific in their action on various lipoproteins.The venom enzyme hydrolyzed phosphatidylcholine and phosphatidylethanolamine at equivalent rates in egg yolk suspensions in isotonic saline or rat brain homogenates in isotonic sucrose, while the enzyme from beef pancreas preferentially attacked phosphatidylethanolamine in these lipoproteins. The pancreatic enzymes were more effective in producing lysophosphatides in brain homogenates than the venom phospholipase A2, and the specific activity of the enzyme from human pancreas was higher with this substrate than any other. It also hydrolyzed phosphatidylethanolamine at a more rapid rate than other phospholipids, including phosphatidylcholine, phosphatidylserine, and the ethanolamine plasmalogens. Lysophosphatide production was assessed quantitatively in the experiments involving the egg yolk and brain homogenate preparations.
The Formation of Homoserine from Methionine in Germinating Peas
Authors: Grant D. R. , Voelkert E.
Published: December 2009

L-Methionine-1-14C was fed through the roots to 6-day-old pea seedlings. After 10 h over 80% of the absorbed radioactivity was recovered in the free amino acid fraction, 8% in the extracted proteins, 5% as carbon dioxide, and 2.2% in the organic acid fractions. Analysis of the amino acids revealed that only 24% of the total activity was recovered as methionine, 40% as homoserine, 10% as isoleucine, and smaller but significant amounts of aspartate, O-acetylhomoserine, and cystathionine. Dilution values strongly imply that aspartate is not an intermediate in the extensive conversion of methionine to homoserine; rather a more direct pathway is involved.
Differential Effects of Growth Hormone and Hydrocortisone on Nuclear RNA Synthesis in Rat Liver
Authors: Ip Peter M. K. , Brossard Maurice
Published: December 2009

RNA has been isolated and fractionated from rat liver nuclei by a sequence of salt extractions into four subfractions: namely nucleoplasmic, deoxyribonucleoprotein-associated, ribonucleoprotein-associated, and nucleolar fractions.Study of 14C-methyl-methionine labeling indicates that the nucleolar RNA fraction isolated by the present procedure is, in fact, of nucleolar origin while the other three fractions are essentially of extranucleolar origin.The effects of growth hormone and hydrocortisone on the nuclear RNA synthesis have been further studied using the present isolation and double-labeling techniques. Both hormones cause an increase in the incorporation of labeled orotic acid into all types of RNA in all four nuclear subfractions. However, the stimulatory effect of growth hormone is found mainly in the 18–28 S and 45–60 S regions of the nucleolar fraction and in regions of the entire gradient of the nucleoplasmic fraction, whereas the stimulatory effect of hydrocortisone is localized mainly in the 10–28 S regions of the nucleolar fraction and in the 4 S and 10–18 S regions of the ribonucleoprotein fraction.The present report suggests that there are qualitative as well as quantitative differences in the action of growth hormone and hydrocortisone on the synthesis of RNA in liver nucleus. The mode of action of the two hormones is discussed.
Immunotolerance to Insulin and Freund's Adjuvant
Authors: Moloney P. J. , Evans M. A.
Published: December 2009

Prior injections of incomplete Freund's Adjuvant with saline did not suppress antibody formation by ox insulin. This finding is in contrast to that of Jankovic (Colloq. Int. Cent. Nat. Rech. Sci. 116, 187 (1963)), namely that prior injection of complete Freund's Adjuvant suppressed antibody formation to bovine serum albumin. The essential factor in the induction of tolerance to insulin by injection of maleyl insulin in incomplete Freund's Adjuvant is maleyl insulin.
Erythrocyte Lipids of Atlantic Cod, Gadus morhua
Authors: Addison R. F. , Ackman R. G.
Published: December 2009

Erythrocytes from mature male cod, which had been starved for 1 week, contained 16.5 × 10−13 g lipid per cell, about 75% of which was phospholipid. Cholesterol represented about 11%, triglycerides 5%, free fatty acids 4%, and sterol esters 2% of the total lipid. The fatty acid composition was typical of a marine lipid, and in general erythrocyte lipids closely resembled cod muscle (cellular) lipid.
Agents Affecting Lipid Metabolism. XL. Effect of Ethyl Chlorophenoxyisobutyrate on Liver Lipids and Serum Lipoproteins in Rats
Authors: Hill P. , Dvornik D.
Published: December 2009

Ethyl p-chlorophenoxyisobutyrate (CPIB) was fed to albino rats at 0.25% of the diet for 21 days. In accordance with earlier findings, treatment (a) decreased the incorporation into cholesterol of acetate and to a lesser extent of mevalonate, and (b) increased the liver weight and its contents of phospholipids and cholesterol. Serum phospholipids were decreased in both lipoprotein fractions separated with dextran sulfate. Incorporation data with labelled precursors suggest increased hepatic synthesis of phospholipids in rats fed CPIB. The release from the liver and the rate of clearance of newly biosynthesized phospholipid and protein moieties of serum lipoproteins were essentially similar to untreated controls.
Further Investigations on Transcription and Translation in Limnaea Embryos
Authors: Brahmachary R. L. , Palchoudhury S. R.
Published: December 2009

14C-amino acid incorporation in uncleaved Limnaea eggs is slight but it slowly increases up to the trochophore stage followed by a rapid rise during the veliger stage when 32P incorporation is falling. There is a peak in the 10 S region of the sucrose density gradient profile of morula RNA. Presumably this morula RNA (messenger RNA) is necessary for final development and hatching of the veliger. The trochophore 10 S peak is the largest, stable and strongly depressed by actinomycin; on the contrary, the veliger 10 S RNA peak is insensitive to actinomycin and seems to be meant for immediate translation.Actinomycin treatment of the uncleaved eggs prevents cleavage in a certain percentage of eggs but in the rest the treatment is not effective until the trochophore stage.
An Atypical Substrate–inhibitor–Rate Relationship for the Action of Antimycin A on the Succinate–Ferricyanide Reductase Activity of Beef Heart Electron Transfer Particles
Authors: Perry G. L. , Williams G. R.
Published: December 2009

The degree of inhibition of the succinate–ferricyanide reductase activity of beef heart electron transfer particles by antimycin A is negligible at low succinate concentrations (< 1 mM) but increases to about 40% at saturating concentrations of succinate. This behavior is explained on the basis of a random order mechanism for the primary dehydrogenase with alternative routes from the monosubstrate complexes, only one of which is sensitive to antimycin.
Inhibition of Fatty Acid Synthetase in Halobacterium cutirubrum and Escherichia coli by High Salt Concentrations
Authors: Pugh E. L. , Wassef M. K. , Kates M.
Published: December 2009

A cell-free enzyme preparation from Halobacterium cutirubrum was shown to catalyze the biosynthesis of fatty acids from malonyl-CoA at zero sodium chloride concentration, with a specific activity about [Formula: see text] that of a similarly prepared fatty acid synthetase from E. coli. Both the H. cutirubrum synthetase and that from E. coli were strongly inhibited by high sodium chloride or potassium chloride concentrations (0.5–4 M). The malonyl-CoA: ACP transacylase, which catalyzes the first step in the fatty acid biosynthetic pathway, was shown to be strongly inhibited by salt in H. cutirubrum, but not in E. coli. It is concluded that H. cutirubrum contains a fatty acid synthetase system which normally operates at a very low level of activity as a result of inhibition by the high intracellular salt concentration present in this organism.
The Amino Acid Sequence of Streptomyces griseus Protease A: The Peptic Peptides
Authors: Johnson P. , Smillie L. B.
Published: December 2009

The peptic peptides of Streptomyces griseus Protease A (excluding the previously characterized disulfide bridge peptic peptides) were fractionated into basic, neutral, and neutral plus acidic peptide fractions by chromatography on Dowex 1 × 2. These three peptide fractions were then fractionated by cation-exchange chromatography on Chromobead P resin using the Technicon autoanalyzer system. Following further purifications on paper, the amino acid compositions and sequences of the peptic peptides were determined. The N-terminal sequence of Protease A has been identified as Ile–Ala–Gly–Gly–Glu–Ala. The numbers of amino acid residues obtained from the amino acid sequences reported are in agreement with those numbers obtained from amino acid analysis of the total protein in the cases of tryptophan, methionine, histidine, proline, phenylalanine, and glutamic acid. Some of the results suggest either the presence of nonidentical but highly homologous proteins in the Protease A preparation or the possibility of repeating sequences in a single molecular species.
Specific Labelling of the Curare Binding Sites of Acetylcholinesterase and Some Properties of the Modified Enzyme
Authors: Belleau B. , DiTullio V.
Published: December 2009

Electric eel acetylcholinesterase was found to selectively react covalently with two molecules of labelled N,N-dimethyl-2-phenylaziridinium chloride (14C-DPA) per unit of 65 000 daltons. One molecule of bound DPA is selectively labilized at pH 9.5. Both alkylated enzyme species (E.2DPA and E.DPA) are inactive toward acetylcholine as substrate, but considerably more reactive toward indophenylacetate (IPA) as substrate. The IPA activities of both the E.2DPA and E.DPA enzymes are unaffected by decamethonium bromide (C10), whereas only the latter suffers inhibition by d-tubocurarine. It is concluded that the enzyme moiety where quaternary effectors interact possesses two topographically distinct classes of sites: one class is essential for C10 inhibition of the esteratic activity, and the other would serve as an allosteric binding site for curare. This latter site may play the role of receptor on excitable membranes.
The Kinetics of the Formation of the Primary Lactoperoxidase – Hydrogen Peroxide Compound
Authors: Maguire R. James , Dunford H. Brian , Morrison Martin
Published: December 2009

The kinetics of the formation of the primary lactoperoxidase – hydrogen peroxide compound (compound I) at 25 °C have been studied over the pH range 3.0–10.8 by steady state methods. The second-order rate constant k1 is pH-independent over the pH region investigated, having a value of (9.2 ± 0.9) × 106M−1s−1. An anomalous effect of formate buffer on the kinetics of the formation of compound I is reported.
Platelet Aggregation: Induction By Means Of a Complex Between Endotoxin and Copper (Cu2+)
Authors: Lewis A. F. , Dickson R. C.
Published: December 2009

The presence of a complex formed between bacterial endotoxin and cupric ion (Cu2+) causes mammalian (human, pig, and rabbit) blood platelets to aggregate in suspension. Complexes formed between endotoxin and Zn2+, Co2+, Ni2+, Mn2+, Fe3+, Ca2+, Mg2+, Ba2+, Al3+, Be2+, Pb2+, Cd2+, Ag+, or Hg2+ do not cause aggregation. The initial stage of the aggregation induced by the complex is not inhibited by inhibitors of adenosine diphosphate (ADP) or collagen induced aggregation, and is not accompanied by release of measureable amounts of serotonin or ADP. The potential clinical significance of the phenomenon is noted.
Turnover of Purine Nucleotides in Rabbit Erythrocytes: Lack of In Vivo Effect of the Nucleoside Transport Inhibitor, p-Nitrobenzyl-6-thioguanosine
Authors: Brown R. R. , Paterson A. R. P.
Published: December 2009

The turnover of purine nucleotides in rabbit erythrocytes in vivo was studied by following the decline with time in the erythrocyte content of 14C-purine metabolites; the half-times of 14C-metabolites of adenine-8-14C and guanine-8-14C were about 30 h and 6 h, respectively. The possibility that purine nucleosides external to the erythrocyte might be involved in nucleotide turnover was tested in experiments which measured the effect on turnover of the inhibitor of nucleoside transport, p-nitrobenzyl-6-thioguanosine. This compound profoundly inhibited a transport-dependent aspect of nucleoside metabolism in erythrocytes, the formation of inosine from externally provided hypoxanthine and guanosine. However, only minor effects on turnover of labelled purine metabolites resulted from treatment of erythrocytes either in vitro or in vivo with the nucleoside transport inhibitor. Multiple intravenous injections of the inhibitor blocked nucleoside transport in erythrocytes, but had only minor effects on the turnover of metabolites of adenine and guanine. It is concluded that purine nucleosides per se are not importantly involved in the turnover of erythrocyte nucleotide pools.
In Vitro Induction of Tyrosine Aminotransferase in Liver Slices by Hydrocortisone
Authors: Liberti J. P. , DuVall C. H. , Wood D. M.
Published: December 2009

A liver slice system has been developed which actively incorporates labeled precursors into RNA and protein for as long as 10 h of incubation. The addition of glucocorticoid induces tyrosine aminotransferase (TA) in liver slices of hypophysectomized rats but not in liver homogenates of hypophysectomized rats or in slices derived from normal rats. TA activity is increased two- to sixfold during 6 h of incubation, the maximal response being observed with 10−6 M steroid. Addition of cydoheximide, at a concentration which depresses protein synthesis 95%, blocks the accumulation of TA. The half-life [Formula: see text] of induced TA is approximately 2–3 h and is similar to that of the basal, noninduced system. These data indicate that glucocorticoid acts only to increase the rate of TA synthesis without affecting its rate of degradation.