bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitochondrial deoxyribonucleic acid from Tetrahymena pyriformis and its kinetic complexity
Authors: Flavell R. A. , Jones I. G.
Published: August 2015

1. Mitochondrial DNA from Tetrahymena pyriformis strain T has a buoyant density (ρ) of 1.685 compared with ρ1.688 for whole cell DNA. Mitochondrial preparations from T. pyriformis strain W show an enrichment of a light satellite (ρ1.686), although this is not obtained free from nuclear DNA (ρ1.692). 2. T. pyriformis mitochondrial DNA renatures rapidly and the kinetics of this process indicate a complexity of approx. 3×107 daltons. 3. The base-pairing in the renaturation product is of a precise nature, since the ‘melting’ temperature (80.5°C) is indistinguishable from that of the native DNA (80.5°C). 4. Centrifugation of mitochondrial DNA in an alkaline caesium chloride density gradient gives two bands, implying the separation of the complementary strands.
Turnover of the glycerolipids of pumpkin leaves. The importance of phosphatidylcholine
Authors: Roughan P. G.
Published: August 2015

Between 1 and 5% of the 14C recovered from pumpkin leaves within 15–60min after pulse-labelling with 14CO2 was in the lipids. The specific radioactivity of the phospholipids was higher than that of the glycolipids. Phosphatidylcholine had five times the specific radioactivity of monogalactosyl diglyceride, and the specific radioactivity of neither galactolipid changed significantly between 1 and 48h after labelling. It therefore seemed unlikely that the galactose moieties of the galactolipids were involved in the transport of assimilated compounds across the chloroplast membrane. Within 60min of the application of [1-14C]acetate to the surfaces of mature, intact pumpkin leaves 70% of the recovered 14C was in the lipid fraction. Of the separated glycerolipids, phosphatidylcholine had by far the highest specific radioactivity at the shorter time-intervals, and the glycolipids again had the lowest specific radioactivities. Phosphatidylcholine was the only lipid to show a significant turnover of radiocarbon as judged by the decrease in specific radioactivity with time. From a comparison of the changes with time of the labelling of fatty acid fractions from phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and monogalactosyl diglyceride, it is suggested that the primary site of linolenic acid biosynthesis in leaf cells is within the phosphatidylcholine molecule.
The uptake of [3H]uridine into the nucleic acids of rat uterus during early pregnancy
Authors: Heald P. J. , O'grady J. E.
Published: August 2015

1. Changes in content and uptake of [3H]uridine into the nucleic acids of rat uterus during the first 9 days of pregnancy were studied. 2. From day 6 implantation sites were separated from the rest of the uterine tissue for independent analysis. 3. Up to day 5 of pregnancy no changes were found in the total dry matter or in RNA and DNA content/unit dry matter nor in the RNA/DNA ratios. 4. From day 6, when implantation sites are visible, the water content of the implantation sites increased by 2–3%, and the RNA content/unit dry wt. and the RNA/DNA ratios increased. The DNA content/unit dry wt. did not increase in the implantation sites until day 8. 5. Uptake of [3H]uridine into the acid-soluble fraction of the tissues was markedly higher in implantation sites than in non-implantation sites. 6. Uptake of [3H]uridine into RNA was significantly increased on day 3 of pregnancy and again on day 5. 7. On days 6 and 7, the incorporation into RNA of implantation sites was significantly higher than in the remainder of the uterine tissue but decreased on days 8 and 9 to the same value as that of the normal tissue. 8. No change occurred in uptake into DNA until day 6, when there was an increase in uptake by the implantation sites. 9. It is suggested that the increase in RNA synthesis on day 3 is a preparation of the uterus for the onset of implantation on day 5, and that increased synthesis in implantation sites on days 6 and 7 is the elaboration of new RNA necessary for this early stage of pregnancy to commence.
Protein-hydrocarbon interactions. Interactions of various proteins with decane in the presence of alcohols
Authors: Cecil R. , Louis C. F.
Published: August 2015

1. Solutions of proteins were subjected to gentle agitation in the presence of small quantities of decane containing different alcohols. 2. Some of the protein was lost from solution and adsorbed on the surface of the emulsion formed; at the same time some decane was bound to the protein remaining in solution. 3. Comparison of these results with those obtained with pure decane suggests that a mixed film of protein+alcohol is formed on the surface of the emulsion. 4. If the concentration of alcohol in decane is increased the amount of protein adsorbed on the emulsion is decreased. This phenomenon was used to compare the effect of different alcohols in disrupting the hydrophobic interactions between proteins and hydrocarbons.
The oxidation products of crude mesobilirubinogen
Authors: Stoll M. S. , Gray C. H.
Published: August 2015

Bile pigment esters were separated by ascending t.l.c. Apparently pure pigments, obtained by ferric chloride oxidation of crude mesobilirubinogen, derived from commercial bilirubin by reduction with sodium amalgam, were shown to be complex mixtures. Successive chromatography of their dimethyl esters on silica gel in methyl acetate–methyl propionate–dichloromethane–carbon tetrachloride (1:1:1:1, by vol.), ethyl methyl ketone–1,2-dichloroethane (1:2, v/v) and benzene–ethanol (100:3, v/v) revealed two major blue pigments (verdins), six major violet pigments (violins) and a red pigment (rhodin) together with numerous minor components. i-Urobilin dimethyl ester, prepared from mesobilirubinogen by dehydrogenation with aqueous iodine, was resolved into three major and at least four minor components on silica gel–kieselguhr (3:1, w/w) in benzene–ethanol (25:2, v/v). The chemical nature of these pigments was investigated by oxidation, by visible and u.v. spectroscopy, by mass spectrometry and by n.m.r. spectrometry. The evidence suggests unusual rearrangement of bilirubin during reduction leading to the formation of IIIα and XIIIα isomers. Isomeric forms of mesobiliviolin IXα and of i-urobilin IXα may also be formed.
Biosynthesis of caffeine in tea callus tissue
Authors: Ogutuga D. B. A. , Northcote D. H.
Published: August 2015

1. A study of caffeine biosynthesis has been made by following the incorporation of radioactive carbon dioxide and methionine into the methylated purines produced by tea callus tissue. 2. The uptake of the radioactive labels into nucleic acid and caffeine was followed over a period of approximately 9h. 3. The distribution of the radioactive labels in both nucleic acid and caffeine was determined after incorporation and subsequent incubation of the tissue in a non-radioactive medium. 4. The results of the experiments indicated that the caffeine arose from purines released from the breakdown of nucleic acids rather than that it was formed directly from a purine pool. 5. A metabolic scheme to show the production of caffeine from the nucleotides of the nucleic acid is discussed.
Physical properties of ribosomal ribonucleic acid isolated from bacteria deficient in ribonuclease I
Authors: Cammack K. A. , Miller D. S. , Grinstead K. H.
Published: August 2015

1. Bacteria deficient in ribonuclease I were used as a source of stable ribosomal RNA. RNA was isolated from a ribosome fraction of Pseudomonas fluorescens N.C.I.B. 8248 and acetone-treated cells of Escherichia coli M.R.E. 600 by the method developed by Robinson & Wade (1968). 2. The s20,w of the 16S and 23S components can vary from 21S and 28S down to 4S depending on the RNA macro-ion concentration and the extent to which charge is suppressed by univalent Na+ and tris+ counter-ions or neutralized through the binding of bivalent Mg2+ to phosphate groups. 3. The primary charge effect in sedimentation and the frictional coefficient (which increases as the molecular conformation expands) both increase with charge and cause a decrease in s value. 4. RNA solutions heated to 80°C for 10min show minor changes in s value and a detectable increase in polydispersity. Millimolar concentrations of Mg2+ promote heat-instability and so does treatment of RNA solutions with the nuclease adsorbent macaloid, which was found to contaminate the solutions with Mg2+. 5. The stabilization of secondary structure by univalent and bivalent cations was investigated by optical methods. 6. The sedimentation properties of 30S and 50S ribosomal subunits and their constituent 16S and 23S RNA components were compared and discussed from the viewpoint of unfolding.
The primary structure of alamethicin
Authors: Payne J. W. , Jakes R. , Hartley B. S.
Published: August 2015

Alamethicin, an antibiotic that can transport cations and induce action potentials in synthetic membranes, is shown to be a cyclic peptide with 18 residues including 7-α-aminoisobutyric acid residues, two glutamine residues and one free carboxyl group. The composition indicates microheterogeneity. Alamethicin itself and many peptides derived from it are immune to enzymic digestion, but specific partial acid cleavages have allowed determination of the complete sequence. Diborane reduction has shown that the α-carboxyl group of glutamine-18 is free, but the ring is formed by a peptide bond between the imino group of proline-1 and the γ-carboxyl group of glutamic acid-17. The structure is contrasted with that of other cation-transporting antibiotics. Model building allows a structure that could stack to form a tunnel with a lipophilic exterior and hydrophilic interior and flexible internal arms formed by the pendant C-terminal glutamine residue.
Proteolytic enzymes of Saccharomyces carlsbergensis
Authors: Maddox I. S. , Hough J. S.
Published: August 2015

1. Of four proteolytic enzymes isolated from autolysing Saccharomyces carlsbergensis, one is inactivated at about 45°C, whereas the others are stable at 50°C. pH optima for activity are from 3.0 to 8.0 but maximum stability is between pH6.0 and 6.5. All appear to be glycoproteins, the carbohydrate moiety containing glucose and mannose residues. 2. Lysed protoplasts of the same yeast release four proteolytic enzymes each of which have two pH optima at pH3.0 and 7.0 approximately. Compared with the enzymes from autolysed yeast, resistance to high temperature is much less, and they are not glycoprotein in nature. 3. The same yeast grown with N-acetyltyrosine ethyl ester as nitrogen source secretes into the medium four proteases believed to be glycoprotein in nature. Generally they resemble the enzymes from lysed protoplasts more than those from autolysing yeast.
The enzymic oxidation of glutathione in rat liver homogenates
Authors: Jocelyn P. C.
Published: August 2015

1. The aerobic oxidation of GSH and other thiols by rat liver homogenate is abolished either by previous dialysis or by removal of the proteins but is restored by a mixture of the protein-free filtrate and the dialysed homogenate. 2. The oxidation is prevented by previously heating the dialysed homogenate but not the protein-free filtrate and also by known inhibitors of xanthine oxidase. 3. A similar oxidation occurs with hypoxanthine in place of of protein-free filtrate.
The effect of semicarbazide on the nature and stability of collagen fibrils
Authors: Ayad Shirley , Wynn C. H.
Published: August 2015

Semicarbazide affected both the final width and stability of fibrils reconstituted from solutions of acid-soluble collagen. Fibril width was increased after semicarbazide treatment at pH2.6 and 4.3, whereas after treatment at pH8.9 it decreased. Fibril stability was decreased after semicarbazide treatment at all values of pH and temperature, indicating the inhibition of intermolecular cross-linking. A direct binding of semicarbazide to the αβ-unsaturated aldehyde groups in the intramolecular cross-link was demonstrated.
An examination of the inhibitory effects of N-iodoacetylglucosamine on Escherichia coli and isolation of resistant mutants
Authors: White R. J. , Kent P. W.
Published: August 2015

1. After incubation of Escherichia coli with N-iodo[1,2-14C2]acetylglucosamine, 95–99% of the 14C taken up by whole cells is located in a cold-trichloroacetic acid-soluble fraction. Two major components of this fraction are S-carboxymethylcysteine and S-carboxymethylglutathione. The same compounds accumulate during incubation with iodo[14C]acetate but not with iodo[14C]acetamide. The amount of 14C associated with a cold-trichloroacetic acid-insoluble fraction are comparable for all three alkylating agents. After incubation with iodo[14C]acetamide, 50% of the label bound to whole cells is recoverable in a cold-trichloroacetic acid-insoluble fraction. 2. Uptake and incorporation of 14C from [U-14C]glycerol is blocked at an early stage by N-iodoacetylglucosamine. No specific inhibition of macromolecular synthesis could be demonstrated. 3. Mutants selected for resistance to iodoacetate are partially resistant to iodoacetate and N-iodoacetylglucosamine, but show no resistance to iodoacetamide. 4. Mutants selected for resistance to N-iodoacetylglucosamine are not resistant to iodoacetate or iodoacetamide, and are defective in their ability to grow on N-acetylglucosamine. Resistance to N-iodoacetylglucosamine is not absolute, and depends on the presence of glucose or certain other sugars; there is no resistance during growth on maltose, glycerol or succinate. 5. Absolute resistance can be achieved by selecting for a second mutation conferring resistance during growth on maltose; double mutants isolated by this procedure are unable to grow on N-acetylglucosamine and grow poorly on glucosamine. Resistant single mutants have a slightly diminished uptake of N-acetyl[1-14C]glucosamine, but in resistant double mutants the uptake of both [1-14C]glucosamine and N-acetyl[1-14C]glucosamine is severely diminished. 6. These observations are consistent with the presence of two permeases for N-acetylglucosamine, one that also permits uptake of glucosamine and another that allows entry of methyl 2-acetamido-2-deoxy-α-d-glucoside. N-Iodoacetylglucosamine can gain entry to the cell by both permeases.
The characterization of undecaprenol of Lactobacillus plantarum
Authors: Gough Doreen P. , Kirby Alison L. , Richards J. B. , Hemming F. W.
Published: August 2015

Evidence for the presence of undecaprenol in the unsaponifiable lipid of Lactobacillus plantarum (N.C.I.B. 6376) is presented. Characterization of the compound was based mainly on mass, i.r. and n.m.r. spectrometry. The prenol was isolated at a concentration of 40μg/g wet wt. of bacteria and contained over 90% (1.0–5.4% of the dose) of the 14C present in the unsaponifiable lipid after incubation of the bacteria with [2-14C]mevalonate. N.m.r. spectrometry indicated the presence of two internal trans-, one α-cis- and seven internal cis-isoprene residues per molecule. The 3H/14C ratios of the prenol after incubation of the bacteria with [2-14C,(4R)-4-3H1]- and [2-14C,(4S)-4-3H1]-mevalonate were in agreement with this stereochemistry. There was no evidence of saturated isoprene residues in the molecule. The undecaprenol appeared to be accompanied by much smaller quantities of decaprenol and nonaprenol.
The influence of electrical stimulation in vitro on protein synthesis and other metabolic parameters of rat extensor digitorum longus muscle
Authors: Pain Virginia M. , Manchester K. L.
Published: August 2015

1. Apparatus is described in which rat extensor digitorum longus muscle can be incubated in buffer under conditions of light tension and be subject to contractures induced by electrical stimulation in vitro. Under these conditions the tissue retains its weight, its content of potassium and size of the extracellular space at values similar to those in vivo. 2. Though uptake of glucose was enhanced on addition of insulin, there was little increase in glucose consumption on stimulation. Breakdown of glycogen and enhancement of lactate output were found on stimulation. 3. Incorporation into protein of several labelled amino acids was diminished during stimulation. Accumulation of [14C]leucine was enhanced whereas that of glycine was decreased. 4. There were no very consistent changes in the content of free unlabelled amino acids during incubation with or without stimulation. Comparison of actual amino acid concentrations in tissue and incubation mixture with accumulation of 14C-labelled amino acid indicated that full equilibration of the cell pool of amino amino acids with the medium is slow. 5. Substantial oxidation of several 14C-labelled acids was observed. 6. The ATP content of the tissue declined a little during incubation and somewhat faster after a period of stimulation. 7. The results are discussed in relation to the way in which exercise can induce muscle hypertrophy.
Quantitative and metabolic changes of hepatic collagens in rats after carbon tetrachloride poisoning
Authors: Hirayama Chisato , Morotomi Ikuo , Hiroshige Kaichiro
Published: August 2015

1. The collagen hydroxyproline in rat liver was composed of 3.5% neutral-soluble collagen, 4.9% acid-soluble collagen and 91.6% insoluble collagen. In labelling studies with [14C]proline in vitro, the specific radioactivities of neutral-soluble, acid-soluble and insoluble collagens in rat liver were found to be 233000, 69000 and 830d.p.m./μmol of hydroxyproline respectively after 1h. 2. During subacute carbon tetrachloride poisoning the hepatic content of insoluble collagen markedly increased, whereas those of soluble collagens did not change. During recovery from subacute poisoning hepatic contents of soluble collagens were markedly decreased. 3. After 8 weeks of carbon tetrachloride poisoning the specific radioactivities of hepatic soluble collagens increased, while that of insoluble collagen decreased. During recovery from subacute poisoning, the specific radioactivities of soluble collagens decreased to the normal range and that of insoluble collagen further decreased. 4. Hepatic collagenolytic activity solubilizing insoluble collagen, which differs from mammalian collagenase, decreased under the conditions of the subacute poisoning and also during recovery from subacute poisoning.
Specificity of action of adrenocorticotrophin in vitro on ascorbate transport in rat adrenal glands
Authors: Clayman M. , Tsang D. , De Nicola A. F. , Johnstone R. M.
Published: August 2015

The inhibition of ascorbate transport by rat adrenal quarters in response to steroidogenesis in vitro was shown to be highly specific with respect to tissue, substrate and steroidogenic agent. The transport system in vitro is capable of net accumulation of ascorbate. The evidence is consistent with the conclusion that ascorbate `depletion' in the adrenal gland is due to a specific block by corticoids of the uptake of ascorbate.
The wall content and composition of Bacillus subtilis var. niger grown in a chemostat
Authors: Ellwood D. C.
Published: August 2015

Bacillus subtilis var. niger was grown in a chemostat with various growth limitations and at various growth rates. The wall content and composition of the organism grown under these conditions were determined. The wall content, expressed as a percentage of the dry weight of organisms, varied with the growth rate. Analysis of wall samples showed that their composition also varied, particularly with respect to the phosphorus content. Wall samples extracted with trichloroacetic acid under carefully controlled conditions were found to contain various amounts of phosphorus, this being present as a glycerol phosphate polymer containing hexose (glucose and in some cases galactose), i.e. a teichoic aid. Teichoic acids were present in the walls of organisms grown under all conditions except when phosphorus limited growth. Then a different anionic polymer, composed of glucuronic acid and N-acetylgalactosamine (a teichuronic acid), was present. Under the specific growth conditions at pH7.0 and 35°C in a chemostat, teichoic acid and teichuronic acid appeared to be mutually exclusive.
Lipid metabolism in the perfused chicken liver. The uptake and metabolism of oleic acid, elaidic acid, cis-vaccenic acid, trans-vaccenic acid and stearic acid
Authors: Bickerstaffe R. , Annison E. F.
Published: August 2015

Comparative studies were made of the uptake and metabolism of cis- and trans-octadecenoic acids by the perfused chicken liver. No differences were observed in the rates of uptake of the isomers. There was considerable incorporation of radioactivity into triglycerides and phospholipids, and some release of labelled lipid into the perfusate was observed. The cis-fatty acids were more readily incorporated into triglycerides than phospholipids, the reverse being true of the trans-fatty acids. Examination of the intramolecular distribution of fatty acids in triglycerides showed that the trans-fatty acid and stearate mainly occupied the 1- and 3-positions, and cis-fatty acids the 2-position. In the phospholipids phosphatidylcholine and phosphatidylethanolamine the trans-fatty acids again behaved like stearic acid and favoured the 1-position. No evidence was obtained of atypical patterns of uptake or metabolism of the trans-fatty acids.
Isolation of bacilysin and a new amino acid from culture filtrates of Bacillus subtilis
Authors: Walker J. E. , Abraham E. P.
Published: August 2015

1. Bacilysin, a labile dipeptide antibiotic that lyses growing staphylococci, was isolated from culture fluids of Bacillus subtilis by a process giving higher yields than those previously obtained. 2. The process involves adsorption on a cation-exchange resin and elution with aqueous trimethylamine, separation from neutral amino acids and glutamic acid by chromatography on DEAE-Sephadex at pH8.7 and separation from other neutral peptides by chromatography in aqueous propan-2-ol on Sephadex G-25. 3. A new amino acid, which is chemically related to bacilysin, was isolated from the fraction containing neutral amino acids. 4. Two substances that yield alanine on hydrolysis, in addition to bacilysin, were obtained from the neutral peptide fraction.
Enzymes of glucose metabolism in normal mouse pancreatic islets
Authors: Ashcroft S. J. H. , Randle P. J.
Published: August 2015

1. Glucose-phosphorylating and glucose 6-phosphatase activities, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, NADP+-linked isocitrate dehydrogenase, `malic' enzyme and pyruvate carboxylase were assayed in homogenates of normal mouse islets. 2. Two glucose-phosphorylating activities were detected; the major activity had Km 0.075mm for glucose and was inhibited by glucose 6-phosphate (non-competitive with glucose) and mannoheptulose (competitive with glucose). The other (minor) activity had a high Km for glucose (mean value 16mm) and was apparently not inhibited by glucose 6-phosphate. 3. Glucose 6-phosphatase activity was present in amounts comparable with the total glucose-phosphorylating activity, with Km 1mm for glucose 6-phosphate. Glucose was an inhibitor and the inhibition showed mixed kinetics. No inhibition of glucose 6-phosphate hydrolysis was observed with mannose, citrate or tolbutamide. The inhibition by glucose was not reversed by mannoheptulose. 4. 6-Phosphogluconate dehydrogenase had Km values of 2.5 and 21μm for NADP+ and 6-phosphogluconate respectively. 5. Glucose 6-phosphate dehydrogenase had Km values of 4 and 22μm for NADP+ and glucose 6-phosphate. The Km for glucose 6-phosphate was considerably below the intra-islet concentration of glucose 6-phosphate at physiological extracellular glucose concentrations. The enzyme had no apparent requirement for cations. Of a number of possible modifiers of glucose 6-phosphate dehydrogenase, only NADPH was inhibitory. The inhibition by NADPH was competitive with NADP+ and apparently mixed with respect to glucose 6-phosphate. 6. NADP+–isocitrate dehydrogenase was present but the islet homogenate contained little, if any, `malic' enzyme. The presence of pyruvate carboxylase was also demonstrated. 7. The results obtained are discussed with reference to glucose phosphorylation and glucose 6-phosphate oxidation in the intact mouse islet, and the possible nature of the β-cell glucoreceptor mechanism.
The effect of a cross-bridging thiol reagent on the catecholamine fluxes of adrenal medulla vesicles
Authors: Hasselbach W. , Taugner G.
Published: August 2015

The thiol groups of the vesicular protein of bovine adrenal medulla were allowed to react with the bifunctional thiol reagent bis-(N-maleimidomethyl) ether and with the monofunctional thiol reagent N-ethylmaleimide, and the ATP-dependent and -independent catecholamine fluxes of the modified preparations were studied. 1. During the initial phase of the reaction bis-(N-maleimidomethyl) ether blocks twice as many thiol groups as does N-ethylmaleimide at equimolar concentrations. 2. Labelling of the bis-(N-maleimidomethyl) ether–protein compound with [14C]-cysteine shows that 70–80% of the blocked thiol groups are interconnected by the bifunctional thiol reagent. 3. At a low extent of reaction (1.5mol of thiol groups/106g of protein) the catecholamine efflux is diminished. If more than 2mol of thiol groups/106g of protein are blocked, the efflux is enhanced whichever thiol reagent is applied. 4. If 2–4mol of thiol groups/106g of protein are blocked the inhibition of the catecholamine influx increases linearly with the proportion of the thiol groups blocked. 5. ATP protects the catecholamine influx and the adenosine triphosphatase activity against bis-(N-maleimidomethyl) ether poisoning somewhat less effectively than against N-ethylmaleimide poisoning.
Possible inhibitory effect of teichoic acid on Bacillus subtilis transfer ribonucleic acid
Authors: Youatt Jean , Montoya Alice , Nester E. W.
Published: August 2015

1. tRNA of Bacillus subtilis was found to be variably contaminated with membrane teichoic acid. 2. Samples with high contents of teichoic acid showed no accepting activity for tRNAPhe and tRNATyr. 3. Removal of teichoic acid restored accepting activity and fractions containing teichoic acid, separated on Sephadex G-150, inhibited the charging of tRNATyr. 4. The presence of teichoic acid did not inhibit the charging of tRNAHis.
Tryptophan catabolism during sporulation in Bacillus cereus
Authors: Prasad Chandan , Srinivasan V. R.
Published: August 2015

1. Two intermediates of tryptophan catabolism were isolated from a sporulating culture of Bacillus cereus and identified as anthranilic acid and kynurenine by their spectral properties. 2. During sporulation the rate of formation of anthranilic acid and kynurenine by whole cells increased and reached a maximum at the pre-spore stage. 3. The specific activities of tryptophan pyrrolase and formylase also increased during sporulation and exhibited a maximal activity at the pre-spore stage. 4. Kynureninase activity reached a maximum during early stages of sporulation and then started to decline. 5. There was a net increase in the activity of tryptophan pyrrolase when cells were grown in the presence of l-tryptophan or dl-kynurenine. 6. The cultures exhibited the maximal activity of kynureninase 2h earlier in the presence of dl-kynurenine whereas l-tryptophan delayed the appearance of the maximal activity by 2h. 7. The omission of glucose from the medium had no effect on the pattern of development of tryptophan pyrrolase during growth and sporulation. 8. On the addition of tryptophan to a chemically defined medium no significant change in the pattern of development of tryptophan pyrrolase was observed.
Ferrochelatase of Rhodopseudomonas spheroides
Authors: Jones M. S. , Jones O. T. G.
Published: August 2015

Extracts of Rhodopseudomonas spheroides contain two ferrochelatases: one is soluble and forms metalloporphyrins from deuteroporphyrin and haematoporphyrin; the other is particulate and forms metalloporphyrins from protoporphyrin, mesoporphyrin, deuteroporphyrin and haematoporphyrin. Neither enzyme incorporates Mg2+ into porphyrins or Fe2+ into porphyrin cytochrome c. By using the particulate enzyme, plots of 1/v versus 1/s when one substrate was varied and the other kept constant showed that neither substrate affected the Km of the other. The suggested sequential mechanism for the reaction is supported by derivative plots of slopes and intercepts. The Km for deuteroporphyrin was 21.3μm and that for Co2+ was 6.13μm. The enzyme incorporated Co2+, Fe2+, Zn2+, Ni2+ and Mn2+; Cd2+ was not incorporated and was an inhibitor, competitive with respect to Co2+, non-competitive with respect to deuteroporphyrin. The Ki for Cd2+ was 0.73μm. Ferrochelatase was inhibited by protohaem, non-competitively with respect to Co2+ or with respect to deuteroporphyrin. Inhibition by magnesium protoporphyrin was non-competitive with respect to deuteroporphyrin, uncompetitive with respect to Co2+. The inhibitory concentrations of the metalloporphyrins are lower than those required for the inhibition of δ-aminolaevulate synthetase by protohaem. Fe2+ is not incorporated aerobically into porphyrins unless an electron donor, succinate or NADH, is supplied; the low aerobic rate of metalloporphyrin synthesis obtained is insensitive to rotenone and antimycin. The rate of Fe3+ incorporation increases as anaerobic conditions are achieved.
Biochemical aspects associated with an ethanol-induced fatty liver
Authors: Walker Jennifer E. C. , Gordon Ellen R.
Published: August 2015

Isocaloric replacement of either the fat or carbohydrate content of the diet by ethanol (36% of the total caloric intake) produced fatty infiltration of the liver in rats. The increase in hepatic triglyceride content was associated with a decrease in both ATP and glycogen contents. Increased activity of mitochondrial Mg2+-stimulated adenosine triphosphatase paralleled the increase in the free Pi content of the liver homogenate. During the regression of the fatty liver, glycogen contents returned to normal within 24h of the removal of ethanol from the diet. Not until the third day after the withdrawal of ethanol had the Mg2+-stimulated adenosine triphosphatase activity and free Pi content of the homogenate returned to normal. A slow regression of the triglyceride content from the liver occurred and by the fifth day both ATP and triglyceride concentrations had returned to the values observed in the rats given the liquid control diet.
Autolysis of isolated cell walls of Bacillus licheniformis N.C.T.C. 6346 and Bacillus subtilis Marburg strain 168. Separation of the products and characterization of the mucopeptide fragments
Authors: Hughes R. C.
Published: August 2015

1. Cell walls were isolated from Bacillus licheniformis N.C.T.C. 6346 and Bacillus subtilis Marburg strain 168 trp grown on casein hydrolysate into exponential phase. Autolysis was carried out and the soluble products, separated by chromatography on DEAE-cellulose, from the two wall preparations are broadly similar in composition and are in agreement with autolysis proceeding with hydrolysis of amide bonds between l-alanine and N-acetylmuramic acid residues in the mucopeptide components. 2. Peptides originating from the mucopeptide components were isolated and shown to be a monomer peptide, l-alanyl-d-glutamyl-meso-diaminopimelic acid and a dimer peptide containing two monomer peptides linked through a residue of d-alanine. Approximately one amide group is present for each equivalent tripeptide unit and is probably substituted on diaminopimelic acid residues. 3. Oligosaccharides originating from the mucopeptide components were isolated and after hydrolysis contained almost equimolar amounts of glucosamine and muramic acid and only very small amounts of amino acids. The number-average chain length, estimated by the release of non-reducing end groups of N-acetylglucosamine with exo-β-N-acetylglucosaminidase, is approximately ten hexosamine residues for oligosaccharides isolated from either organism. The oligosaccharides are polydisperse. 4. N-Acetylglucosamine residues are the only reducing terminals detectable in the oligosaccharides isolated from B. subtilis or B. licheniformis cell-wall autolysates. The number-average chain lengths of the oligosaccharides were determined by estimation of the content of these residues and are higher than those found by enzymic assay. Possible reasons for the discrepancy are discussed.
A study of calf thymus histone fraction F2(b) by gel filtration
Authors: Edwards P. A. , Shooter K. V.
Published: August 2015

The gel-filtration behaviour of calf thymus histone fraction F2(b) was studied at three different salt concentrations (0.01m-, 0.10m- and 1.00m-sodium chloride) and two different pH ranges (pH3–4 and pH6.7–7.1). Other histone fractions [F1, F2(a) and F3] were also utilized to assist interpretation of the data. It was found that the Stokes radius of histone fraction F2(b) was not significantly changed when the salt concentration was increased, implying that the aggregation of the individual histone molecules (Edwards & Shooter, 1969) resulted in only relatively minor changes in the hydrodynamic volume. Aggregation would appear to be due to the salting out of hydrophobic regions giving rise, in the aggregate, to a compact core of hydrophobic groups from which protrude the remaining basic parts of the molecule. Repulsion between charged groups on the basic regions of individual histone molecules would give the aggregate approximately spherical symmetry, the diameter of the aggregate approximating to the length of a single histone molecule.
Some aspects of the kinetics of rat liver pyruvate carboxylase
Authors: Wimhurst Janet M. , Manchester K. L.
Published: August 2015

1. The kinetics of rat liver pyruvate carboxylase were examined and the effect of various agents as activators or inhibitors determined. 2. Essentially similar results were obtained in comparisons of kinetics determined by a radioactivity method involving extracts of acetone-dried powders from whole livers and with a spectrophotometric assay using partially purified enzyme from the mitochondrial fraction. Activity per g of liver from fed or starved rats assayed under optimum substrate and activator conditions was 3 or 6 μmol of oxaloacetate formed/min at 30°C, respectively. 3. The enzyme exhibited cold-lability and lost activity on standing, even in 1.5m-sucrose. 4. The Km towards pyruvate was about 0.33mm and towards bicarbonate 4.2mm. Km towards MgATP2− was 0.14mm. Mg2+ ions activated the enzyme, in addition to their role in MgATP2− formation. From calculations of likely concentrations of free Mg2+ in the assay medium a Ka towards Mg2+ of about 0.25mm was deduced. Mn2+ also activated the enzyme as well as Mg2+, but at much lower concentrations. It appeared to be inhibitory when concentrations of free Mn2+ as low as 0.1mm were present. 5. Excess of ATP is inhibitory, and this appears at least in part independent of the trapping of Mg2+. 6. Both Co2+ and Zn2+ were inhibitory; 2mol of the latter appeared to be bound even in the presence of excess of Mg2+ and the inhibition was time-dependent. 7. Ca2+ inhibited by competition with Mg2+ (Ki about 0.38mm). The inhibition due to Ca2+ was less pronounced when activation was with Mn2+. Inhibition by Ca2+ and ATP appeared to be additive. 8. Hill plots suggested that no interactions occurred between ATP-binding sites. Although similar plots for total Mg2+ gave n=3.6, no conclusions could be drawn due to the chelation of the cation with other components of the assay. Similar difficulties arose in assessing the values for Ca2+. 9. The enzyme was inactive in the absence of acetyl-CoA and showed a sigmoidal response in its presence. Ka was about 0.1mm with possibly up to four binding sites. Malonyl-CoA was a competitive inhibitor, with Ki 0.01mm. 10. There was no apparent inhibition by glucose, glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-diphosphate, acetoacetate, β-hydroxybutyrate, malate, aspartate, pyruvate, palmitoylcarnitine, octanoate, glutathione, butacaine, triethyltin or potassium chloride under the conditions used. Inhibition was found with citrate (possibly by chelation) and adenosine, and also by phosphoenolpyruvate, AMP, ADP and cyclic AMP, Ki towards the last four being 0.55, 0.76, 0.25 and 1.4mm respectively.
The subcellular localization of di- and tri-peptide hydrolase activity in guinea-pig small intestine
Authors: Peters T. J.
Published: August 2015

1. Two different subcellular fractionation techniques were applied to guinea-pig intestinal mucosa and the composition of the brush borders prepared by the two methods were compared. 2. By using a kinetic assay system the subcellular distribution of activity against ten dipeptides and five tripeptides was studied. 3. Only small amounts (5–10%) of activity against dipeptides were found in the brush-border region, the enzymes being concentrated in the cytosol. 4. Significant amounts (10–60%) of activity against tripeptides were found in the brush border with the remainder largely present in the soluble fraction. 5. The relevance of these studies to the localization in vivo and the possible role of peptidases in protein digestion is discussed.
Effects of progesterone on protein metabolism in chicken oviduct tissue pretreated with oestrogen
Authors: Muller K. R. , Cox R. F. , Carey N. H.
Published: August 2015

1. The effect of simultaneous injections of oestrogen benzoate and progesterone (0.5mg/day each) on immature chicken oviduct tissue pretreated with oestrogen benzoate (0.5mg/day) was studied. 2. After 3 days of treatment with both hormones, the weight of the tissue doubles as compared with tissue treated only with oestradiol benzoate. 3. The progesterone-induced weight increase had no effect on total DNA content of the tissue, but greatly increased the protein/DNA and RNA/DNA ratios. 4. Amino acid incorporation in vivo after progesterone treatment was elevated as measured by using 2h pulses of amino acids; this effect could be accounted for by observed alterations in the concentrations of free amino acids in the tissue. 5. With longer pulses of amino acid the specific radioactivity of total protein remained high in tissue treated with progesterone, at times when specific radioactivity of protein in oestrogen-treated animals was diminishing. 6. From a knowledge of the specific radioactivity of labelled amino acids in the free amino acid pool and in newly synthesized protein, the rate of protein synthesis was estimated in differently treated tissues. 7. The results suggest that progesterone treatment does not cause an increase in protein synthesis. It is concluded that the observed accumulation of oviduct protein is achieved via an effect of progesterone on protein catabolism.
Tamm–Horsfall urinary glycoprotein. The chemical composition
Authors: Fletcher A. P. , Neuberger A. , Ratcliffe Wendy A.
Published: August 2015

1. A revised amino acid and carbohydrate composition of human Tamm–Horsfall glycoprotein is presented. 2. No significant differences were obtained in the amino acid composition of Tamm–Horsfall glycoprotein isolated from patients with cystic fibrosis. 3. The glycoprotein was shown to possess a high half-cystine content of 1 per 11–12 amino acid residues, which has been confirmed by performic acid oxidation and S-alkylation with iodoacetate and iodoacetamide. No thiol groups were detected in the glycoprotein. 4. Treatment of the glycoprotein with 0.5m-sodium hydroxide at 4°C for 2 days did not release heterosaccharide material, which suggests that the predominant carbohydrate–protein linkages present are not of the O-glycosidic type. 5. No N-terminal amino acid was detected in the glycoprotein.
Kinetic studies of formate dehydrogenase
Authors: Peacock D. , Boulter D.
Published: August 2015

1. The kinetic mechanism of formate dehydrogenase is a sequential pathway. 2. The binding of the substrates proceeds in an obligatory order, NAD+ binding first, followed by formate. 3. It seems most likely that the interconversion of the central ternary complex is extremely rapid, and that the rate-limiting step is the formation or possible isomerization of the enzyme–coenzyme complexes. 4. The secondary plots of the inhibitions with HCO3− and NO3− are non-linear, which suggests that more than one molecule of each species is able to bind to the same enzyme form. 5. The rate of the reverse reaction with carbon dioxide at pH6.0 is 20 times that with bicarbonate at pH8.0, although no product inhibition could be detected with carbon dioxide. The low rate of the reverse reaction precluded any steady-state analysis as the enzyme concentrations needed to obtain a measurable rate are of the same order as the Km values for NAD+ and NADH.
The 503nm pigment of Escherichia coli
Authors: Kamitakahara Joyce R. , Polglase W. J.
Published: August 2015

The yield of cell protein was one-third less for streptomycin-dependent Escherichia coli B than for the wild-type parent strain when both were grown aerobically on a medium with limiting glucose, but anaerobically the yield of protein was similar for both strains. The transient pigment absorbing at 503nm that is known to be present in E. coli and other organisms was not detectable in streptomycin-dependent mutants nor in a non-dependent (energy-deficient) revertant. When wild-type E. coli B was grown on limiting glucose–salts medium containing 2,4 dinitrophenol, the yield of cell protein was decreased and formation of the 503nm pigment was inhibited. Fumarase, aconitase and glucose 6-phosphate dehydrogenase were de-repressed in E. coli B cells grown with excess of glucose in a medium containing 2,4-dinitrophenol. In air-oxidized, wild-type E. coli B cells, the 503nm pigment appeared before reduced cytochromes when gluconate was the substrate but failed to appear when succinate was the substrate. The results provide evidence for a role of the 503nm pigment in aerobic energy metabolism, possibly as an electron acceptor from NADPH.
The dissociation of Yoshida hepatoma ribosomes into active particles
Authors: Gravela Enrico
Published: August 2015

1. The sedimentation pattern of Yoshida hepatoma ribosomes shows mainly a high dimer peak and an intermediate peak between those of monomer and dimer. 2. The treatment of the postmitochondrial supernatant with EDTA or potassium chloride leads to the dissociation of ribosomes into subunits, through a decrease ofthe ribosomal Mg2+/phosphorus ratio. Provided that the deprivation of endogenous Mg2+ is not complete, the subunits reassociate into active polyribosomes after addition of magnesium chloride to the medium. If the Mg2+/phosphorus ratio is lowered below 0.01 (μmol/μmol), structural changes occur, that become evident by a loss of protein and by a decreased sedimentation rate, which render the subribosomal particles unable to reassociate. 3. In the re-formation of polyribosomes from subunits, during the progressive increase of the concentration of magnesium chloride in the medium, the formation of monomeric ribosomes seems to be intermediate. 4. A dimerization of monomers and subunits occurs at concentrations of magnesium chloride greater than those required for the re-formation of polyribosomes and a preincubation for 1h at 0°C is necessary for the maximum dimerization, whereas the complete reconstitution of polyribosomes is immediate.
The cross-linking of tyrosine by treatment with tetranitromethane
Authors: Williams J. , Lowe J. M.
Published: August 2015

1. Tyrosine was treated with tetranitromethane. 2. Approx. 10% of the tyrosine was converted into 3-nitrotyrosine. 3. Three fluorescent compounds were also formed. They appear to be a dimer, trimer and tetramer in which tyrosine units are linked by biphenyl bonds. 4. The dimer and trimer have also been isolated from some proteins after treatment with tetranitromethane. 5. The yield of 3-nitrotyrosine from ovotransferrin after treatment with tetranitromethane was much smaller than the loss of tyrosine. 6. Several unidentified compounds were also formed by the reaction between tyrosine and tetranitromethane.
The purification and properties of the l-serine O-sulphate-degrading system of pig liver
Authors: Tudball N. , Thomas P. , Bailey-Wood R.
Published: August 2015

1. The enzyme system from pig liver responsible for the αβ-elimination of l-serine O-sulphate was purified 1000-fold. 2. Isoelectric focusing produced two enzymically active fractions with isoelectric points at pH5.6 and 5.9 respectively. 3. Osmometry and gel filtration showed both enzymes to possess molecular weights of approx. 54000. 4. The separate activities exhibited similar amino acid compositions.
Release of intestinal surface-membrane glycoproteins associated with enzyme activity by brief digestion with papain
Authors: Forstner Gordon G.
Published: August 2015

Rat intestinal surface-membrane glycoproteins were labelled by intraperitoneal injection of [1-14C]glucosamine 4h before the animals were killed. At this time, density-gradient centrifugation of disrupted brush borders indicated that glycoprotein radioactivity was distributed identically with sucrase, a plasma-membrane marker. Labelled brush borders were digested by papain for brief time-intervals known to release surface-enzyme particles without disruption of the unit membrane. Digestion for 5min released 90% of the surface sucrase, and almost one-half of the brush-border glycoprotein and label. On Sepharose 4B column chromatography most of the glycoprotein and label emerged as a single peak. This peak contained the most actively labelled glycoprotein in the brush border and was closely associated with maltase, sucrase, β-naphthylamidase and alkaline phosphatase. The peak was partially resolved on polyacrylamide-gel electrophoresis into three bands. Each band contained a distinctive enzyme or enzyme pair, and was labelled by [1-14C]glucosamine. No periodic acid–Schiff-negative protein was observed in the peak material. Glycoproteins susceptible to brief digestion with papain are therefore closely linked to released surface-enzyme particles. Intestinal surface glycoproteins are heterogeneous with respect to molecular weight, electrophoretic mobility and function.
Regulation of dipicolinic acid biosynthesis in sporulating Bacillus cereus. Characterization of enzymic changes and analysis of mutants
Authors: Forman M. , Aronson A.
Published: August 2015

Some of the early enzymes in the lysine-biosynthetic pathway also function for dipicolinic acid synthesis in sporulating Bacillus cereus T. 1. The first enzyme, aspartokinase, loses its sensitivity to feedback inhibition by lysing. This change occurs before the time of dipicolinic acid synthesis but at a time when diaminopimelic acid is required for spore cortex formation. 2. A possible regulatory change at a branch point in the pathway was studied by examining the properties of a key enzyme, dihydrodipicolinic acid reductase. No alteration in the feedback sensitivity or sedimentation rate of this enzyme could be detected during sporulation. 3. Two mutants producing heat-sensitive spores were analysed. Both produced spores that contained decreased amounts of dipicolinic acid. Although neither was a lysine auxotroph, they both had greatly decreased activities of certain lysine-biosynthetic enzymes in sporulating cells. 4. Starvation of cells for calcium also results in the production of spores that are heat-sensitive and contain less dipicolinic acid than the control. A decreased content of one of the lysine-biosynthetic enzymes, dihydrodipicolinic acid synthetase, in calcium-starved cells could account for the lower concentration of dipicolinic acid in the spores.