bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein aggregation. Studies of larger aggregates of C-phycocyanin
Authors: Lee J. J. , Berns D. S.
Published: August 2015

Aggregates of phycocyanin sedimenting at 17s, 22s and 27s are demonstrated to constitute more than 40% of crude blue–green-algal extracts, pH6·0 and I0·1, and are retained in highly purified preparations. Sedimentation-velocity studies of the large aggregates as a function of pH are reported. Sucrose-density-gradient experiments performed as a function of time of sedimentation indicate that: (1) with increasing time of sedimentation, the largest aggregates are dissipated at the leading protein boundary and the several phycocyanin species present are not completely resolved; (2) phycocyanin fractions with the largest aggregates exhibit the highest E620/E280 ratio and the largest relative fluorescence efficiency. Gel-filtration experiments with Sephadex G-200 do not resolve the species completely, and reapplication of phycocyanin gel-filtration fractions to the column results in an elution pattern similar to the original, except that there is an enhancement of the allophycocyanin fraction and the amount of denatured protein. Increasing the sedimentation times in a sucrose density gradient also enhances the allophycocyanin fraction. Fluorescence results demonstrate that there are possibly three excitation maxima, one corresponding to the monomer (approx. 600mμ), one for higher aggregates (625–630mμ) and one for the allophycocyanin fraction (approx. 650mμ). Only a single fluorescence-emission band is detected, which is fairly symmetrical and which has a red shift with higher aggregation and with the appearance of allophycocyanin. The appearance of allophycocyanin may be correlated with the irreversible disaggregation of the largest phycocyanin species. It is suggested that the largest protein aggregates are in the size range of the biliprotein aggregates reported in electron microscopy of algal cells.
Protein aggregation. The effect of deuterium oxide on large protein aggregates of C-phycocyanin
Authors: Lee J. J. , Berns D. S.
Published: August 2015

The amount of 11s aggregate in phycocyanin, normally stimulated by hydrophobic forces, is dramatically increased by the presence of deuterium oxide. Proteins in which hydrophobic forces are not proposed as a mechanism for aggregation are unaffected by deuterium oxide. These observations are consistent with the lower critical micelle concentration reported for ionic detergents in deuterium oxide. Phycocyanin samples containing a majority of material sedimenting faster than 11s were also investigated in the presence of deuterium oxide with the following findings: the most rapidly sedimenting species in water buffer is 24s; in deuterium oxide more than 10% of the protein sediments at 67s and substantial amounts of other species with sedimentation coefficients larger than 24s are present. These large quantities of species sedimenting faster than 24s are found in deuterium oxide buffers from pD5·5 to 7·0. Sucrose-density-gradient studies in deuterium oxide at pD6·0 confirm the presence of large amounts of more rapidly sedimenting species. Spectrophotometric studies on fractions from the sucrose-density-gradient experiments indicate with the presence of higher aggregates a red shift of the visible-absorption maximum and an enhancement of the E620/E280 ratio. Fluorescence-emission studies show a greater relative fluorescence efficiency for these higher aggregates and are consistent with the suggested enhancement of higher aggregates in deuterium oxide. The existence of phycocyanin aggregates of such a large size is suggested to be of importance in vivo, with phycocyanin playing a role as a structural protein.
A study by polyacrylamide-gel electrophoresis of the effect of proteolysis on Micrococcus lysodeikticus polynucleotide phosphorylase
Authors: Fitt P. S. , Fitt E. A. , Wille H.
Published: August 2015

1. Trypsin digestion of Micrococcus lysodeikticus polynucleotide phosphorylase (nucleoside diphosphate–polynucleotide nucleotidyltransferase) causes a progressive increase in electrophoretic mobility in polyacrylamide gels of the single active degradation product. 2. A marked increase in primer requirement for CDP polymerization occurs before a more mobile product is formed. 3. α-Chymotrypsin digestion yields a product that separates into several active species on polyacrylamide-gel electrophoretograms. 4. No separation of ADP-and CDP-polymerization activities occurs during electrophoresis after either trypsin or α-chymotrypsin treatment.
The stoicheiometry of electron transfer by bacterial and plant ferredoxins
Authors: Evans M. C. W. , Hall D O , Bothe H , Whatley F R
Published: August 2015

1. The number of electrons carried by ferredoxins from spinach, the blue–green alga Anacystis nidulans, the anaerobic bacterium Clostridium welchii and the photosynthetic bacterium Chromatium was determined. 2. Ferredoxins were reduced by illuminated chloroplasts, and the stoicheiometry of the reoxidation in the dark of the ferredoxins by NADP and benzyl viologen was measured. 3. Spinach and A. nidulans ferredoxins were found to be one-electron carriers, and Cl. welchii and Chromatium ferredoxins were two-electron carriers.
Biochemical effects of the hypoglycaemic compound pent-4-enoic acid and related non-hypoglycaemic fatty acids. Oxidative phosphorylation and mitochondrial oxidation of pyruvate, 3-hydroxybutyrate and tricarboxylic acid-cycle intermediates
Authors: Senior A. E. , Sherratt H. S. A.
Published: August 2015

1. The effects of the hypoglycaemic compound pent-4-enoic acid, and of four structurally related non-hypoglycaemic compounds (pent-2-enoic acid, pentanoic acid, cyclopropanecarboxylic acid and cyclobutanecarboxylic acid), on several reactions in rat liver mitochondria were determined. 2. The use of manometric techniques for measurements of oxidations and of phosphorylation is critically discussed. 3. Pent-4-enoic acid and pentanoic acid uncoupled oxidative phosphorylation at low concentrations, but usually by not more than about 50%. 4. All the compounds, except cyclobutanecarboxylic acid, strongly inhibited the oxidation of pyruvate and 2-oxoglutarate, but the oxidations of succinate, citrate and 3-hydroxybutyrate were not strongly inhibited. 5. All the compounds, except cyclobutanecarboxylic acid, inhibited decarboxylation of [1−14C]pyruvate with ferricyanide as electron acceptor. 6. All the compounds, except pent-2-enoic acid, caused mitochondrial swelling after a time-lag.
Biochemical effects of the hypoglycaemic compound pent-4-enoic acid and related non-hypoglycaemic fatty acids. Carbohydrate metabolism
Authors: Senior A. E. , Sherratt H. S. A.
Published: August 2015

1. The effects of the hypoglycaemic compound, pent-4-enoic acid, and of four structurally related non-hypoglycaemic compounds (pent-2-enoic acid, pentanoic acid, cyclopropanecarboxylic acid and cyclobutanecarboxylic acid), on glycolysis, glucose oxidation and gluconeogenesis in some rat tissues were determined. 2. None of the compounds at low concentrations inhibited glycolysis by particle-free supernatant fractions from rat liver, skeletal muscle and intestinal mucosa, though there was inhibition by cyclopropanecarboxylic acid and cyclobutanecarboxylic acid at 3mm concentration. 3. Pent-4-enoic inhibited the oxidation of [1−14C]palmitate by rat liver slices, but did not increase the oxidation of [U−14C]glucose. 4. Pent-4-enoic acid (0·01mm) strongly inhibited gluconeogenesis by rat kidney slices from pyruvate or succinate, but none of the other compounds inhibited significantly at low concentrations. 5. There was also some inhibition of gluconeogenesis in kidney slices from rats injected with pent-4-enoic acid. 6. The mechanism of the hypoglycaemic effect of pent-4-enoic acid is discussed; it is suggested that there is an inhibition of fatty acid and ketone-body oxidation and of gluconeogenesis so that glucose reserves become exhausted, leading to hypoglycaemia. 7. The mechanism of the hypoglycaemic action of pent-4-enoic acid appears to be similar to that of hypoglycin.
The metabolism of glucose in diaphragm muscle from normal rats, from streptozotocin-treated diabetic rats and from rats treated with anti-insulin serum
Authors: Beloff-Chain Anne , Rookledge K. A.
Published: August 2015

1. The metabolism of [U−14C]glucose by the isolated diaphragm muscle of normal rats, rats rendered diabetic with streptozotocin and rats with transitory insulin deficiency after an injection of anti-insulin serum was studied. 2. The incorporation of [14C]glucose into glycogen and oligosaccharides was significantly decreased in the diabetic diaphragm muscle and in the muscle from rats treated with anti-insulin serum. 3. Neither diabetes nor transitory insulin deficiency influenced the oxidation of glucose, or the formation of lactate and hexose phosphate esters from glucose. 4. Insulin fully restored the incorporation of glucose into glycogen and maltotetraose in the diabetic muscle, but the incorporation into oligosaccharides, although increased in the presence of insulin, was significantly lower than the values obtained with normal diaphragm in the presence of insulin.
The biosynthesis of the wall teichoic acid in Staphylococcus lactis I3
Authors: Baddiley J , Blumsom N. L. , Douglas L. Julia
Published: August 2015

1. The biosynthesis of the wall teichoic acid in Staphylococcus lactis I3 was studied. Cell-free particulate enzyme preparations, probably representing fragmented membrane, were isolated and used for the synthesis of polymer. 2. By using appropriately labelled CDP-glycerol and UDP-N-acetylglucosamine it was shown that the former contributes a glycerol phosphate residue and the latter contributes an N-acetylglucosamine 1-phosphate residue to the repeating unit. 3. No polymer was synthesized unless both nucleotides were present, and no other substrates were required. 4. The properties of the enzyme system were studied. 5. Although attempts to fractionate the system failed, the biosynthesis is believed to be complex and its mechanism is considered.
Positive control of sulphate reduction in Escherichia coli. Isolation, characterization and mapping of cysteineless mutants of E. coli K 12
Authors: Jones-Mortimer M. C.
Published: August 2015

To determine to what extent the biosynthesis of cysteine in Escherichia coli resembles that in Salmonella typhimurium, the following experiments were performed. (1) Mutants of E. coli K 12 deficient in the biosynthesis of cysteine were isolated. (2) These mutants were classified by nutritional and biochemical criteria; some mutants lacked a single enzyme of sulphate reduction, other mutants appeared to lack two or more enzymes. (3) The genetic map predicted from the biochemical data alone is shown to be incorrect, and an alternative map, consistent with the genetic data, is proposed for the cys mutants of E. coli.
Positive control of sulphate reduction in Escherichia coli. The nature of the pleiotropic cysteineless mutants of E. coli K 12
Authors: Jones-Mortimer M. C.
Published: August 2015

1. The function of the wild-type alleles of the pleiotropic mutants cysB and cysE of Escherichia coli was investigated. 2. The wild-type allele cysB+ is dominant to the mutant allele cysB in stable and transient heterozygotes. 3. The wild-type allele cysE+ is dominant to the mutant allele cysE, as predicted. 4. Sulphur-starved cultures of cysB or cysE strains contain less than 0·2nmole of free cysteine/mg. dry wt. 5. Complementation in vitro is not observed between extracts of cysB mutants and mutants lacking sulphite reductase only. 6. A scheme, involving positive control of the enzymes of sulphate activation and reduction, is suggested to account for the control of cysteine biosynthesis.
Purification of a diketo acid hydrolase from rat liver and its use for the enzymic determination of 3,5-dioxohexanoate (triacetate)
Authors: Brock D. J. H. , Williamson D. H.
Published: August 2015

1. A diketo acid hydrolase was purified about 100-fold from rat liver and some of its properties were studied. 2. Comparison of its activity with 3,5-dioxohexanoate (triacetate) and fumarylacetoacetate at various stages during the purification suggests that it is identical with 4-fumarylacetoacetate fumarylhydrolase. 3. The acetoacetate formed on cleavage of 3,5-dioxohexanoate by the hydrolase can be determined either with 3-hydroxybutyrate dehydrogenase or with 3-oxo acid CoA-transferase and 3-hydroxyacyl-CoA dehydrogenase. These reactions form the basis of enzymic assays for 3,5-dioxohexanoate.
Carbohydrate formation from various precursors in neonatal rat liver
Authors: Vernon R. G. , Eaton Susan W. , Walker D G
Published: August 2015

1. Measurements of the net synthesis of glucose plus glycogen from various precursors in slices of glycogen-depleted livers from rats at various stages of development indicated an increase in the gluconeogenic capacity after birth with l-lactate, oxaloacetate, a casein hydrolysate, l-serine, l-threonine, l-alanine and glycerol as substrates. 2. The highest rates of incorporation of 14C-labelled precursors into glucose plus glycogen in slices of normal livers of rats of various ages were observed in such tissue preparations from neonatal animals for an amino acid mixture, l-alanine, l-serine and l-threonine. 3. The activities of rat hepatic l-serine dehydratase and l-threonine dehydratase increase rapidly after birth and show maxima about 20 days later. 4. The results provide further evidence of the increased capacity for hepatic gluconeogenesis in the neonatal period and suggest various sites of regulation of the process.
The availability of carnitine acetyltransferase in mitochondria from guinea-pig liver and other tissues
Authors: Barker P. J. , Fincham N. J. , Hardwick D C
Published: August 2015

The carnitine acetyltransferase and glutamate dehydrogenase activities of guinea-pig liver and other tissues were estimated. Both enzymes are wholly mitochondrial, and can only be fully observed after disruption of the mitochondrion. Triton X-100 (0·1%) or freeze-drying revealed more activity than other methods tried. In mitochondria prepared and suspended in 0·25m-sucrose and in cell cytoplasm only small fractions of the total enzymic activity could be observed in guinea-pig liver: on average 7·5% of carnitine acetyltransferase and 5·5% of glutamate dehydrogenase. It is concluded that, in liver or mammary gland of goat, guinea pig or rat, little or no carnitine acetyltransferase is available in vivo to acetyl-CoA outside the mitochondrion.
Clearing-factor lipase in adipose tissue. Distinction of different states of the enzyme and the possible role of the fat cell in the maintenance of tissue activity
Authors: Cunningham V. J. , Robinson D S
Published: August 2015

1. Incubation of intact epididymal adipose tissue from fed rats at 37° in an albumin solution at pH7·4 in vitro results in rapid loss of clearing-factor lipase activity until a low activity, stable to prolonged incubation, is attained. The clearing-factor lipase activity of intact tissue from starved rats, which is initially much less than that of tissue from fed rats, is mainly stable to incubation at 37°. 2. Much of the clearing-factor lipase activity of intact epididymal adipose tissue from fed rats is inactivated by collagenase. The enzyme activity of intact tissue from starved rats is not inactivated by collagenase. 3. The clearing-factor lipase activity of fat cells isolated from the epididymal adipose tissue of fed rats is stable to prolonged incubation at 37°. It represents only a small proportion of the total activity of the intact tissue. In starved rats, the isolated fat cells contain a much higher proportion of the activity of the intact tissue. Their activity is also stable at 37°. 4. Incubation of isolated fat cells in a serum-based medium leads to a progressive rise in clearing-factor lipase activity. Actinomycin increases the extent of this rise in activity. No rise in clearing-factor lipase activity occurs when stromal-vascular cells isolated from epididymal adipose tissue are incubated in the medium. 5. The findings indicate that less than 20% of the activity of intact adipose tissue from fed rats is retained when fat cells are isolated from the tissue by collagenase treatment. The activity that is lost could be that which normally functions in the uptake of triglyceride fatty acids by the tissue.
The metabolism of d-glyceraldehyde by the lens
Authors: Van Heyningen Ruth
Published: August 2015

1. The metabolism of d-glyceraldehyde by the lens was examined. 2. When low concentrations of d-[U−14C]glyceraldehyde were incubated with lens extracts there was no incorporation of the label into protein; more than two-thirds of the labelled metabolites consisted of glyceric acid and glycerol, their relative proportions depending on the species. Lactic acid, a phosphate, glutathione–glyceraldehyde compounds and a neutral compound were also formed. 3. When high concentrations of d-[U−14C]glyceraldehyde were incubated with lens, extensive incorporation of the label into protein occurred and the protein became yellow–brown. This coloured protein did not exhibit the fluorescent properties shown by the brown proteins of human cataractous senile lens, or of naphthaquinone-treated lens. 4. Evidence that d-glyceraldehyde is formed by the lens was sought but not found.
Studies on the effect of vitamin D on calcium absorption and transport
Authors: Hashim George , Clark Irwin
Published: August 2015

1. Mucosal cells of the small intestine obtained from rats deprived of vitamin D or given excessive amounts of the vitamin accumulated significantly more calcium than did cells from control animals. 2. Mucosal cells from vitamin D-deficient rats released less calcium than did cells from normal or hypervitaminotic D animals. 3. Studies in vivo showed that the transfer of 45Ca from the intestine to the blood was delayed in vitamin D deficiency, but was accelerated in hypervitaminosis D. 4. The findings support the thesis that vitamin D is involved in the release of calcium rather than in its uptake by mucosal cells. 5. Further evidence is presented suggesting that uptake of calcium by intestinal mucosal cells at 0° is primarily passive, whereas at 38° uptake and release are effected by an active process that depends on energy derived from glycolytic activity.
Enzymic changes in rabbit and rat mammary gland during the lactation cycle
Authors: Gul Bilquis , Dils R.
Published: August 2015

1. Activities of glucose 6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), isocitrate dehydrogenase (EC 1.1.1.42), malate dehydrogenase (EC 1.1.1.37), malate dehydrogenase (decarboxylating) (EC 1.1.1.40), and pyruvate carboxylase (EC 6.4.1.1) were determined in subcellular fractions of mammary gland from rabbits during pregnancy, at different stages of lactation and during weaning. The results were compared with those obtained in similar experiments with rat mammary gland. 2. Three bases of expression of the activity of enzymes in the particle-free supernatant fraction of mammary gland were compared. During lactation, activity expressed per mg. of particle-free supernatant protein (uncorrected for milk protein) correlated well with that expressed per μg. of DNA phosphorus. The disadvantages of expressing activities per g. wet wt. are discussed. 3. The major differences between the two tissues were: (a) neither malate dehydrogenase (decarboxylating) nor a soluble form of pyruvate carboxylase could be detected in rabbit mammary gland at any stage of the lactation cycle; (b) isocitrate dehydrogenase increased in activity during lactation in rabbit mammary gland, but not in that of the rat. 4. Pyruvate carboxylase in the mitochondrial fraction of rabbit mammary gland, and in both the mitochondrial and the soluble fractions of rat mammary gland, did not change in activity during lactation. 5. For each tissue, the NADP-dependent dehydrogenases studied had a high activity at all stages of the lactation cycle compared with the rate of fatty acid synthesis at mid-lactation. The significance of these results is discussed with respect to the supply of NADPH via NADH.
Brain arylamidase. Purification and characterization of the soluble bovine enzyme
Authors: Brecher A. S. , Suszkiw J. B.
Published: August 2015

1. An enzyme acting on aminoacyl-β-naphthylamides has been isolated from the soluble fraction of bovine brain and purified 205-fold by means of ammonium sulphate fractionation, hydroxyapatite adsorption and DEAE-Sephadex column chromatography. 2. Arylamidase requires thiol groups for retention of its activity, is heat-labile and is susceptible to freezing. p-Chloromercuribenzoate and N-ethylmaleimide inactivate the enzyme rapidly. 3. Metal ions are not required for its activity, but stimulation by Mn2+ and Mg2+ and inactivation by Co2+ and Zn2+ are observed. 4. Optimum pH7·5 in phosphate buffer was exhibited for all substrates tested except l-leucyl-β-naphthylamide, for which optimum pH is 6·5. 5. Km values for a number of substrates have been obtained and substrate inhibition at high concentrations was demonstrated. 6. The molecular weight is approx. 70000 as determined by Sephadex-gel filtration.
Conformation changes and dissociation of Fc fragments of rabbit immunoglobulin G as a function of pH
Authors: Charlwood P. A. , Utsumi S.
Published: August 2015

1. The sedimentation coefficients of rabbit immunoglobulin G, four types of Fc fragments, univalent Fab and bivalent F(ab)2 fragments were measured as a function of pH. 2. In conjunction with molecular-weight determinations by sedimentation equilibrium, and with the behaviour on gel filtration, this enabled the state of association of the Fc fragments to be followed. 3. The type possessing an interchain disulphide bond, 1Fc fragment, changed extensively in structure, but not in molecular weight. 4. There was good correlation between the readiness to dissociate and the chain length of the shorter Fc fragments that do not contain the interchain covalent bond. 5. The increasing resistance to dissociation as the fragments became shorter ran parallel with the ability to resist enzymic attack. 6. The site of the strong association between component chains of Fc fragment is located in the C-terminal half. 7. The gel-filtration behaviour of the Fc fragments clearly confirms that the process is governed by the Stokes radius rather than molecular weight. 8. The ultracentrifugal results were used to estimate the separations of the hydrodynamic subunits in intact immunoglobulin G, and as a basis for a schematic structure.
Behaviour of α-aminoadipylcysteine and glutamylcysteine in the presence of intact and disrupted mycelium of a Cephalosporium sp
Authors: Loder P. Bronwen , Abraham E P , Newton G. G. F.
Published: August 2015

1. δ-(l-α-Aminoadipyl)-l-cysteine, the corresponding d- and dl-α-aminoadipyl isomers, δ-(dl-α-amino[6−14C]adipyl)-l-cysteine and γ- and α-l-glutamyl-l-cysteine were synthesized. 2. The behaviour of δ-(l-aminoadipyl)-l-cysteine and the corresponding d- and dl-α-aminoadipyl isomers was studied in the presence of suspensions of intact mycelium of a Cephalosporium sp., suspensions treated ultrasonically and extracts obtained by grinding with alumina. 3. With intact mycelium the l-α-aminoadipyl isomer was removed more rapidly from the extracellular fluid than the corresponding d-isomer. 4. Addition of δ-(dl-α-amino[6−14C]adipyl)-l-cysteine to suspensions of intact mycelium led to the labelling of extracellular and intracellular penicillin N and cephalosporin C, but also to extensive hydrolysis of the dipeptide. 5. Broken-cell systems hydrolysed δ-(l-α-aminoadipyl)-l-cysteine and the corresponding d-α-aminoadipyl isomer, but the former was hydrolysed more readily than the latter. 6. γ- and α-l-Glutamyl-l-cysteine were also hydrolysed but δ-(l-α-aminoadipyl)-l-cysteinyl-l-valine was not. 7. Only part of the enzyme activity in broken-cell systems responsible for the hydrolysis of δ-(α-aminoadipyl)-l-cysteine was present in the supernatant obtained on centrifugation at 20000g. 8. Possible implications of these findings are discussed.
Glycerol kinase activities in muscles from vertebrates and invertebrates
Authors: Newsholme E A , Taylor K.
Published: August 2015

1. Glycerol kinase (EC 2.7.1.30) activity was measured in crude extracts of skeletal muscles by a radiochemical method. The properties of the enzyme from a number of different muscles are very similar to those of the enzyme from rat liver. Glycerol kinase from locust flight muscle was inhibited competitively by l-3-glycerophosphate with a Ki of 4·0×10−4m. 2. The activity of glycerol kinase was measured in a variety of muscles from vertebrates and invertebrates in an attempt to explain the large variation in the activity of this enzyme in different muscles. 3. In vertebrates glycerol kinase activities were generally higher in red muscle than in white muscle; the highest activities (approx. 0·2μmole/min./g. fresh wt.) were found in the red breast muscle of some birds (e.g. pigeon, duck, blue tit) whereas the activities in the white breast muscle of the pheasant and domestic fowl were very low (approx. 0·02μmole/min./g.). 4. On the basis of glycerol kinase activities, muscles from insects can be classified into three groups: muscles that have a low enzyme activity, i.e. <0·3μmole/min./g. (leg muscles of all insects studied and the flight muscles of cockroaches and the tsetse fly); muscles that have an intermediate enzyme activity, i.e. 0·3–1·5μmoles/min./g. (e.g. locusts, cockchafers, moths, water-bugs); and muscles that have a high enzyme activity, i.e. >1·5μmoles/min./g. (e.g. bees, wasps, some blowflies). 5. The function of glycerol kinase in vertebrate and insect muscles that possess a low or intermediate activity is considered to be the removal of glycerol that is produced from lipolysis of triglyceride or diglyceride by the muscle. Therefore in these muscles the activity of glycerol kinase is related to the metabolism of fat, which is used to support sustained muscular activity. A possible regulatory role of glycerol kinase in the initiation of triglyceride or diglyceride lipolysis is discussed. 6. The function of glycerol kinase in the insect muscles that possess a high activity of the enzyme is considered to be related to the high rates of glycolysis that these muscles can perform. The oxidation of extramitochondrial NADH, and therefore the maintenance of glycolysis, is dependent on the functioning of the glycerophosphate cycle; if at any stage of flight (e.g. at the start) the rate of mitochondrial oxidation of l-3-glycerophosphate was less than the activity of the extramitochondrial glycerophosphate dehydrogenase, this compound would accumulate, inhibit the latter enzyme and inhibit glycolysis. It is suggested that such excessive accumulation of l-3-glycerophosphate is prevented by hydrolysis of this compound to glycerol; the latter would have to be removed from the muscle when the accumulation of l-3-glycerophosphate had stopped, and this would explain the presence of glycerol kinase in these muscles and its inhibition by l-3-glycerophosphate.
The influence of the size and nature of basic activators on Clostridium perfringens polynucleotide phosphorylase-catalysed polyadenylic acid synthesis
Authors: Fitt P. S. , Wille Helga
Published: August 2015

1. Basic oligo- and poly-(amino acids) stimulate polyadenylic acid synthesis by purified Clostridium perfringens polynucleotide phosphorylase (nucleoside diphosphate–polyribonucleotide nucleotidyltransferase, EC 2.7.7.8). 2. The effectiveness of the activators increases with chain length up to approx. 20–30 residues. 3. Polymers of the l and dl series are equally effective on a weight-for-weight basis. 4. l-Lysine, d-lysine, diethylamine and triethylamine, as hydrochlorides or hydrobromides, all stimulate the reaction markedly if their concentration is high enough. Their effect is similar to that of sodium chloride. 5. The size of the product depends primarily on the Mg2+ concentration and basic polymers have a relatively limited effect on it. 6. Polyadenylic acid itself undergoes an Mg2+-catalysed non-enzymic hydrolysis.
Factors affecting the activity of pyruvate kinase of Acetobacter xylinum
Authors: Benziman Moshe
Published: August 2015

1. Extracts of Acetobacter xylinum were found to contain the glycolytic enzymes involved in the conversion of triose phosphate into pyruvate. Pyruvate kinase had the lowest relative activity. Phosphofructokinase activity was not detected in the extracts. 2. Only slight differences in the activity of pyruvate kinase were observed between cells grown on glucose and those grown on intermediates of the tricarboxylic acid cycle. 3. Pyruvate kinase, partially purified from ultrasonic extracts by ammonium sulphate fractionation, required Mg2+ ions for activity. It was not activated by K+ or NH4+ ions. 4. The plots representing the relationship between initial velocity and phosphoenolpyruvate concentration were sigmoidal, suggesting a co-operative effect for phosphoenolpyruvate. The Hill coefficient (n) for phosphoenolpyruvate was 2. The rate of the reaction changed with increasing ADP concentrations according to normal Michaelis–Menten kinetics. 5. The enzyme was inhibited by ATP (Ki0·9×10−3m). The inhibition was competitive with regard to ADP but not with regard to phosphoenolpyruvate. It was not relieved by excess of Mg2+ ions. 6. The possible relationship of the properties of pyruvate kinase to regulatory mechanisms for controlling gluconeogenesis and carbohydrate oxidation in A. xylinum is discussed.
Mechanism of non-enzymic transamination reaction between histidine and α-oxoglutaric acid
Authors: Doctor V. M. , Oró J.
Published: August 2015

Non-enzymic transamination reactions at 85° between various amino acids and α-oxoglutaric acid are catalysed by metal ions, e.g. Al3+, Fe2+, Cu2+ and Fe3+. The reaction is optimum at pH4·0. Of the 14 amino acids studied histidine is the most active. In the presence of Al3+ histidine transaminates with α-oxoglutaric acid, forming glutamic acid and Al3+–imidazolylpyruvic acid complex as the end products. However, in the presence of Fe2+ or Cu2+ the products are glutamic acid and a 1:2 metal ion–imidazolylpyruvic acid chelate. The greater effectiveness of histidine in these reactions is attributed to the presence of the tertiary imidazole nitrogen atom, which is involved in the formation of stable sparingly soluble metal ion–imidazolylpyruvic acid complexes or chelates as end products of these reactions. Of the metal ions studied only Al3+, Fe2+, Fe3+ and Cu2+ are effective catalysts for the transamination reactions, and EDTA addition completely inhibits the catalytic effect of the Al3+. Spectrophotometric evidence is presented to demonstrate the presence of metal ion complexes of Schiff bases of histidine as intermediates in the transamination reactions. These results may contribute to understanding the role of histidine in enzyme catalysis.
The structure of an acylated inositol mannoside in the lipids of propionic acid bacteria
Authors: Shaw N. , Dinglinger F.
Published: August 2015

1. Lipids were extracted from five strains of Propionibacterium with chloroform–methanol mixtures and fractionated by chromatography on silicic acid. 2. All five extracts contained a glycolipid composed of fatty acids, inositol and mannose in the molar proportions 2:1:1. 3. Hydrolysis of the glycolipid with alkali gave a mixture of fatty acids and O-α-d-mannopyranosyl-(1→2)-myoinositol. 4. Analysis of the fatty acids by g.l.c. showed that they were predominantly straight- and branched-chain isomers of pentadecanoic acid and heptadecanoic acid. 5. The location and distribution of the fatty acid residues in the molecule was established by periodate oxidation studies and mass spectrometry. The structure of the major glycolipid is 1-O-pentadecanoyl-2-O-(6-O-heptadecanoyl-α-d-mannopyranosyl)myoinositol. 6. The glycolipids are located in the membrane; the cell walls are devoid of lipid. 7. Possible functions of the glycolipid are discussed.
A shift in the optimum pH of phospholipase D produced by activating long-chain anions
Authors: Quarles R. H. , Dawson R. M. C.
Published: August 2015

1. The activity of phospholipase D (phosphatidylcholine phosphatidohydrolase, EC 3.1.4.4) towards ultrasonically treated phosphatidylcholine or large phosphatidylcholine particles activated with ether was maximal near pH5, and there was little activity above pH6. 2. When the enzyme was activated by the addition of phosphatidic acid to large phosphatidylcholine particles the pH optimum was shifted to pH6·5 irrespective of the amount of activator added. 3. When the enzyme was activated with low concentrations of dodecyl sulphate the pH optimum was 5·5 with little activity above pH6. With higher concentrations of dodecyl sulphate the pH–activity profile was shifted upwards towards a pH optimum of 6·5–6·6, the magnitude of the shift depending on the extent of the hydrolysis. 4. The shifts in the pH–activity profiles cannot be correlated with changes in the ‘surface pH’ of the substrate particles calculated from the measurement of their ζ-potentials (electrophoretic mobilities).
Commitment to sporulation in Bacillus subtilis and its relationship to development of actinomycin resistance
Authors: Sterlini Janet M. , Mandelstam J.
Published: August 2015

1. Experiments to determine the point of commitment to sporulation were carried out by restoring nutrients at different times to suspensions of sporulating Bacillus subtilis. 2. No single point of commitment to the process as a whole was found. Instead, the cells became committed in turn to the following successive events connected with sporulation: formation of alkaline phosphatase, development of refractility, synthesis of dipicolinic acid and development of heat-resistance. 3. Each point of commitment was followed within about 30min. by a period in which the event concerned ceased to be inhibited by actinomycin D. 4. The implication of these results is that each point of commitment is probably due to the formation of a species of long-lived messenger RNA and that, in any case, sporulation is regulated at the level of both transcription and translation. 5. It is also shown that sporulation and growth are perhaps not mutually exclusive functions and that histidase, an enzyme typical of the vegetative state, can be induced in sporulating suspensions.
Metabolism of camphors and related compounds
Authors: Robertson J. S. , Hussain M.
Published: August 2015

1. The metabolism of (±)-norcamphor, (+)-camphor, (−)-camphor, (+)-epicamphor, (±)-camphorquinone, (±)-camphane-2,5-dione and camphane was investigated in rabbits. All the compounds except camphane-2,5-dione increased the content of glucuronide in the urine. 2. (±)-Norcamphor was reduced to endo-norborneol; (+)-camphor, contrary to expectation, was reduced to (+)-borneol, as well as being hydroxylated to (+)-5-endo-hydroxycamphor and (+)-3-endo-hydroxycamphor, 5-endo-hydroxycamphor being the predominant product. (+)-Epicamphor was reduced mainly to (+)-epiborneol; (±)-camphorquinone gave 3-endo-hydroxycamphor and 2-endo-hydroxyepicamphor, the former being the major metabolite. (±)-Camphane-2,5-dione was reduced to 5-endo-hydroxycamphor. Camphane was hydroxylated to borneol and epiborneol, the latter predominating. 3. An explanation of these findings is given in terms of steric hindrance and thermodynamic stability. 4. The possibility was investigated that NADH was involved in the reductions.
The determination of the molecular weight of ribonucleic acid by polyacrylamide-gel electrophoresis. The effects of changes in conformation
Authors: Loening U E
Published: August 2015

1. The effects of changes in experimental conditions on the mobility of RNA in polyacrylamide-gel electrophoresis were investigated. 2. The linear relation between log(molecular weight) and electrophoretic mobility was shown to be independent within limits of salt or gel concentration. 3. The relative mobility of RNA with low content of guanylic acid and cytidylic acid residues was decreased in low-ionic-strength buffer. This was related to a small relative decrease in sedimentation coefficient. 4. However, Mg2+ ion caused almost no increase in mobility although it was associated with large increases in sedimentation coefficient. This suggested opposing actions of Mg2+ ion on the size and effective charge of the RNA. 5. It is concluded that the method provides a satisfactory measurement of molecular weight, which is almost independent of the nucleotide composition of RNA at moderate salt concentrations.
The activities of some enzymes concerned with energy metabolism in mammalian muscles of differing pigmentation
Authors: Burleigh I. G. , Schimke R. T.
Published: August 2015

1. Extractable hexokinase activity was measured in the red and white skeletal muscles of the rabbit and in the hearts and diaphragms of four animal species differing markedly in size. Activities vary over a 40-fold range, being least in white skeletal muscle of the laboratory rabbit and greatest in mouse heart. 2. Hexokinase activities correlate approximately with capacities to undertake reactions of the tricarboxylic acid cycle as determined by succinate oxidase assays. Both enzyme activities seem best related to the average contractile-energy expenditure per unit weight of muscle over an extended period, rather than to the rapidity of individual contractions. 3. Hexokinase and succinate oxidase activities cannot be related to a muscle's content of soluble pigment. They display an inverse relationship with activities of phosphorylase and glycolytic enzymes, but only within the group of rabbit skeletal muscles whose oxidative capacities are at the lower end of the observed range. 4. Total glycogen–UDP glucosyltransferase activities do not vary significantly between rabbit skeletal muscles, although those of hexokinase differ by about sixfold. On the average, glucose 6-phosphate is probably oxidized directly. However, observations cited in the literature suggest that muscles with an active hexokinase may well preferentially accumulate glycogen when glucose is present in excess of the fibres' capacity to oxidize it. 5. When considered with published results obtained in vivo, the present findings indicate that phosphorylase has a minor role in the energy expenditure of muscles with a predominantly oxidative metabolism. In these, the major substrates appear to be blood glucose, fatty acids and possibly lipids. 6. The histochemical criteria by which muscle fibres are commonly described as red or white are inadequate.
Lipid peroxide formation in microsomes. The role of non-haem iron
Authors: Wills E. D.
Published: August 2015

1. Metal ion-chelating agents such as EDTA, o-phenanthroline or desferrioxamine inhibit lipid peroxide formation when rat liver microsomes prepared from homogenates made in pure sucrose are incubated with ascorbate or NADPH. 2. Microsomes treated with metal ion-chelating agents do not form peroxide on incubation unless inorganic iron (Fe2+ or Fe3+) in a low concentration is added subsequently. No other metal ion can replace inorganic iron adequately. 3. Microsomes prepared from sucrose homogenates containing EDTA (1mm) do not form lipid peroxide on incubation with ascorbate or NADPH unless Fe2+ is added. Washing the microsomes with sucrose after preparation restores most of the capacity to form lipid peroxide. 4. Lipid peroxide formation in microsomes prepared from sucrose is stimulated to a small extent by inorganic iron but to a greater extent if adenine nucleotides, containing iron compounds as a contaminant, are added. 5. The iron contained in normal microsome preparations exists in haem and in non-haem forms. One non-haem component in which the iron may be linked to phosphate is considered to be essential for both the ascorbate system and NADPH system that catalyse lipid peroxidation in microsomes.
Lipid peroxide formation in microsomes. Relationship of hydroxylation to lipid peroxide formation
Authors: Wills E. D.
Published: August 2015

1. Aminopyrine strongly inhibits NADPH-induced lipid peroxide formation in rat liver microsomes, but ascorbate-induced peroxidation is inhibited to a smaller extent. 2. Aminopyrine oxidation is stimulated by Mg2+ but inhibited by Ca2+. Concentrated solutions (10mm) of iron-chelating agents inhibit aminopyrine oxidation, but the more dilute solutions (0·5mm) of chelators that block lipid peroxide formation do not inhibit aminopyrine oxidation. Microsomes prepared from sucrose–EDTA homogenates rapidly oxidize aminopyrine, but do not form lipid peroxide when incubated with ascorbate or NADPH. 3. Aminopyrine oxidation is strongly inhibited by p-chloromercuribenzoate, less by iodoacetamide and weakly by N-ethylmaleimide. The site of action of these compounds is considered to be a ferredoxin-type protein. GSH and cysteine also inhibit. 4. Other drugs oxidized by microsomes such as caffeine, phenobarbitone and hexobarbitone had either no or little effect on lipid peroxide formation, but codeine inhibited. 5. Most aliphatic hydrocarbons, alcohols, ketones and aldehydes did not affect lipid peroxide formation, but chloroform and carbon tetrachloride inhibited. 6. Many aromatic compounds inhibited lipid peroxide formation. Only aromatic acids were without any effect and phenols and amines were very strong inhibitors. 7. Induction of lipid peroxide formation in microsomes by incubation with ascorbate or NADPH or by treatment with ionizing radiation leads to a sharp decline in the ability of microsomes to oxidize aminopyrine or hydroxylate aniline. 8. It is considered that the two processes of hydroxylation and lipid peroxide formation are closely linked in microsomes. They probably depend on the same electron-transport chain, and peroxide formation, which involves membrane disintegration, may be part of the normal membrane remodelling process.
Nitrite oxidase and nitrate reductase in Nitrobacter agilis
Authors: Faull K. F. , Wallace W. , Nicholas D. J. D.
Published: August 2015

Nitrite oxidase and nitrate reductase in Nitrobacter agilis were shown to be separate enzymes. The best separation of the two systems was achieved by ammonium sulphate fractionation. The effects of various compounds, including antimycin A, 2-n-heptyl-4-hydroxyquinoline N-oxide and chlorate, also clearly distinguish between the two enzyme reactions. The relationship between the two opposing reactions in Nitrobacter is discussed.
Phenol biosynthesis in higher plants. Gallic acid
Authors: Dewick P. M. , Haslam E.
Published: August 2015

The biosynthesis of gallic acid in a number of higher plants was investigated by using l-[U−14C]phenylalanine, (−)-[G−14C]shikimic acid, d-[1−14C]glucose and d-[6−14C]glucose as tracers. The results are compared with those obtained similarly for caffeic acid and are interpreted in terms of the dehydrogenation of 5-dehydroshikimic acid as a normal route of metabolism for gallic acid.
The metabolism of 2-furoic acid by Pseudomonas F2
Authors: Trudgill P W
Published: August 2015

1. Pseudomonas F2 isolated by enrichment culture on 2-furoic acid and grown with it as carbon source oxidized the compound with a Qo2 of 170μl./mg. dry wt./hr. and the overall consumption of 2·5μmoles of oxygen/μmole of substrate. 2. In the presence of 1mm-sodium arsenite, oxygen uptake was restricted to 0·54μmole/μmole of 2-furoate oxidized, with the formation of 0·86μmole of 2-oxoglutarate/μmole of 2-furoate. 3. Cell suspensions, disrupted in a French pressure cell and centrifuged at 27000g, yielded supernatants capable of catalysing the slow oxidation of 2-furoate (0·17μmole/mg. of protein/hr.). 4. Fractionation of 27000g supernatants at 200000g yielded a soluble enzyme fraction capable of catalysing the oxidation of 2-furoate only in the presence of added 200000g pellet or of Methylene Blue. 5. The 2-furoate-stimulated uptake of oxygen or the anaerobic reduction of Methylene Blue by dialysed 27000g supernatant required the addition of ATP and CoA, and the rate of oxygen uptake was further enhanced by the addition of magnesium chloride and NAD+. 6. The role of ATP and CoA in the formation of 2-furoyl-CoA was demonstrated by the accumulation of 2-furoylhydroxamic acid in the presence of hydroxylamine. 7. Dialysed 200000g supernatant, treated with Dowex 1, required the addition of ATP, CoA and Methylene Blue before it could oxidize 2-furoate to 2-oxoglutarate, which was trapped in unitary stoicheiometric yield as its phenylhydrazone. Magnesium chloride and NAD+ were not stimulatory in this system. The oxidation of 2-furoate to 2-oxoglutarate was not inhibited by substrate analogues, metal ion-chelating agents, thiol-active compounds or inhibitors of cytochrome-mediated electron transport. 8. No evidence was obtained for the intervention of 2,5-dioxovalerate as an intermediate in 2-oxoglutarate formation.
Kinetics of thiamin cleavage by sulphite
Authors: Leichter J. , Joslyn M. A.
Published: August 2015

Results are presented on the rate of thiamin cleavage by sulphite in aqueous solutions as affected by temperature (20–70°), pH(2·5–7·0), and variation of the concentration of either thiamin (1–20μm) or sulphite (10–5000μm as sulphur dioxide). Plots of the logarithm of percentage of residual thiamin against time were found to be linear and cleavage thus was first-order with respect to thiamin. At pH5 the rate was also found to be proportional to the sulphite concentration. In the pH region 2·5–7·0 at 25° the rate constant was 50m−1hr.−1 at pH5·5–6·0, and decreased at higher or lower pH values. The rate of reaction increased between 20° and 70°, indicating a heat of activation of 13·6kcal./mole.