bluuebunny/crossref_metadata_2025 huggingface dataset:
Adipose-tissue pyruvate kinase. Properties and interconversion of two active forms
Authors: Pogson C I
Published: August 2015

1. Extraction of rat epididymal adipose tissue with buffer containing EDTA yields a pyruvate kinase, provisionally called PyK-A, the properties of which resemble in several respects those of the allosteric pyruvate kinase of liver. These properties include co-operative interactions with phosphoenolpyruvate, Mg2+, K+, NH4+ and ATP, and sensitivity to activation by fructose 1,6-diphosphate. 2. Extraction in the absence of EDTA yields predominantly a form, PyK-B, that shows both normal Michaelis–Menten kinetics with phosphoenolpyruvate, Mg2+ and ATP, and co-operative interactions with K+ and NH4+; this form is insensitive towards fructose 1,6-diphosphate. 3. Both forms yield simple kinetics with ADP, though Km values differ in the two systems. In all cases where co-operativity has been demonstrated, Hill-plot n values are between 1·4 and 2·0. 4. The conversion of PyK-A into PyK-B is mediated specifically by fructose 1,6-diphosphate; the reverse reaction is occasioned by EDTA, ATP or citrate. It is thought that a bivalent cation may be involved in this interconversion. 5. Attempts at partial purification have revealed that the enzyme resembles the pyruvate kinase of skeletal muscle, rather than that of liver, in its solubility in ammonium sulphate and elution from DEAE-cellulose. 6. The relevance of these properties in the regulation of pyruvate kinase activity in vivo in adipose tissue is discussed.
The carnitine-independent oxidation of palmitate plus malate by moth flight-muscle mitochondria
Authors: Stevenson Edmund
Published: August 2015

Mitochondria isolated from the flight muscle of the southern armyworm moth, Prodenia eridania, can oxidize palmitate+malate very rapidly. Added carnitine had no effect on the rate of oxidation of palmitate+malate by flight-muscle mitochondria from two species of moths, and carnitine palmitoyltransferase could not be detected in Prodenia by direct assay. Palmitoylcarnitine was not oxidized by moth mitochondria, but when added in low concentrations it reversibly suppressed the oxidation of palmitate. The evidence indicates that carnitine is not involved in fatty acid degradation by moth flight muscle. Added thiols, including CoA, also suppressed palmitate+malate oxidation. An ATP-dependent fatty acyl-CoA synthetase is present in moth mitochondria.
Rat small-intestinal β-galactosidases. Kinetic studies with three separated fractions
Authors: Asp Nils-Georg , Dahlqvist Arne
Published: August 2015

1. Three fractions of β-galactosidase activity from the rat small-intestinal mucosa were separated chromatographically. Two of these fractions had an acid pH optimum at 3–4, and the third one had a more neutral pH optimum at 5·7. 2. The two ‘acid’ β-galactosidase fractions had considerably lower Km values for hetero β-galactosides than for lactose. The Vmax. values were similar for all the substrates used (lactose, phenyl β-galactoside, o-nitrophenyl β-galactoside, p-nitrophenyl β-galactoside and 6-bromo-2-naphthyl β-galactoside). No difference could be detected between the two ‘acid’ fractions with respect to their enzymic properties (pH optimum, Km for the different substrates, Ki for lactose as an inhibitor of the hydrolysis of hetero β-galactosides, Ki for phenyl β-galactoside as an inhibitor of the hydrolysis of lactose, and relative Vmax. for the hydrolysis of different substrates). These two fractions probably represent different forms of the same enzyme. 3. The ‘neutral’ fraction had similar Km values for all the substrates hydrolysed, but with lactose as substrate the Vmax. was much higher than with the hetero β-galactosides. This fraction did not split phenyl β-galactoside or 6-bromo-2-naphthyl β-galactoside at a measurable rate. 4. Lactose was a competitive inhibitor of the hetero β-galactosidase activities of all the three fractions, and Ki for lactose as an inhibitor in each case was the same as Km for the lactase activity. Phenyl β-galactoside was a competitive inhibitor of the lactase activity of all the three fractions. These facts strongly indicate that in all the three fractions lactose is hydrolysed by the same active sites as the hetero β-galactosides. 5. Human serum albumin stabilized the separated enzymes against inactivation by freezing and thawing.
The effects of ovariectomy and injected oestradiol monobenzoate on polypeptide metabolism in the hypothalamus
Authors: Hooper K. C.
Published: August 2015

1. The activities of two groups of peptidases separated from a homogenate of rabbit hypothalamus were determined (a) in adult female animals, (b) in ovariectomized animals and (c) in intact female animals after injection of oestradiol monobenzoate (15–120μg.). 2. Ovariectomy decreased the enzyme activity initially; the activity in the particulate group of enzymes subsequently returned to normal whereas the activity of the supernatant fraction was less than normal 8 months after operation. 3. Injection of oestradiol monobenzoate increased the enzyme activity in the supernatant fraction to that observed in pregnant animals and in suckled lactating animals. 4. There is a correlation between changes in enzyme activity of the supernatant fraction and conditions that are known to influence gonadotrophin secretion.
The histones of some human tissues
Authors: MacGillivray A J
Published: August 2015

1. Histones were examined from five human tissues, namely thymus, liver, placenta, bronchial tumour and peripheral leucocytes. 2. The four main histone fractions [F1, F2(b), F2(a), and F3] were isolated and characterized. 3. The amino acid analyses, N-terminal group analyses and electrophoretic patterns were very similar to those of the corresponding fractions of calf thymus. 4. The yields of fractions F1 and F2(b) were high in human thymus, in human bronchial tumour and in some preparations of normal human leucocytes. 5. It is concluded that the pattern of nuclear histones found in lower forms of life was conserved during the evolutionary process leading to man.
Chemical studies on the cysteine and terminal peptides in tryptic digests of actin
Authors: Johnson P. , Perry S V
Published: August 2015

1. On exhaustive digestion of carboxymethylated actin in 6m-urea solutions with carboxypeptidase A, 1 mole of phenylalanine was liberated/43000g. of protein. At a lower urea concentration and in the absence of urea, carboxymethyl-cysteine (CMCys) was also liberated. 2. Three cysteine-containing peptides were identified by the study of peptide ‘maps’ of tryptic digests of actin treated with thiol reagents. 3. The three peptides, each containing one residue of CMCys, were isolated from tryptic digests of carboxymethylated actin by ion-exchange chromatography. 4. One of these peptides was possibly the N-terminal peptide and contained about 17–18 residues; another was CMCys-Asp-Ile-Asp-Ile-Arg; the other, CMCys-Phe, was the C-terminal tryptic peptide. 5. The chemical evidence suggests that the actin molecule consists of a single polypeptide chain of molecular weight about 44000.
The equilibrium constant of the isocitrate dehydrogenase reaction
Authors: Londesborough J. C. , Dalziel K.
Published: August 2015

1. The equilibrium constant for oxidative decarboxylation of isocitrate by NADP+, catalysed by isocitrate dehydrogenase, was measured in solutions of various ionic strengths and at several temperatures. 2. Thermodynamic values for the reaction were obtained by extrapolation to zero ionic strength, and the heat of reaction was estimated. 3. The effect of Mg2+ ion concentration on the equilibrium was studied.
Electron-microscopic and chemical studies of oligomers in horse ferritin
Authors: Williams M. A. , Harrison Pauline M.
Published: August 2015

Horse ferritin was fractionated both by starch-gel electrophoresis and by gel filtration on Sephadex G-200. Monomer fractions contained up to 98% of monomer and oligomer fractions up to 76% of oligomers as determined by quantitative electron microscopy. Percentages obtained from electron micrographs correlated well with analytical starch-gel electrophoretograms and ultracentrifuge patterns. Amino acid analyses of monomer- and oligomer-enriched fractions showed no significant differences. Ferritin oligomers did not apparently dissociate on dilution for electron microscopy or on storage. Apoferritin dimers were stable in 0·01m-phosphate buffer at dilutions down to 0·19mg./ml. as shown by ultracentrifugation. Chemical studies indicated that the intermolecular bonds in oligomers are resistant to a variety of reagents and conditions, including those that would be expected to attack disulphide, peptide and ester linkages respectively. Partial disaggregation was achieved at high pH values and in 67% (v/v) acetic acid. Centre-to-centre intermolecular distances in dimers were found to be about 100å. Three main types of trimer configuration were found and a variety of tetramers and pentamers. These configurations are described and discussed.
Biochemical effects of the hypoglycaemic compound pent-4-enoic acid and related non-hypoglycaemic fatty acids. Fatty acid oxidation
Authors: Senior A. E. , Robson B. , 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 (pentanoic acid, pent-2-enoic acid, cyclopropanecarboxylic acid and cyclobutanecarboxylic acid), on the oxidation of saturated fatty acids by rat liver mitochondria were determined. 2. The formation of 14CO2 from [1−14C]palmitate was strongly inhibited by 0·01mm-pent-4-enoic acid. 3. The inhibition of oxygen uptake was less than that of 14CO2 formation, presumably because fumarate was used as a sparker. 4. The oxidation of [1−14C]-butyrate, -octanoate or -laurate was not strongly inhibited by 0·01mm-pent-4-enoic acid. 5. The other four non-hypoglycaemic compounds did not inhibit the oxidation of any saturated fatty acid when tested at 0·01mm concentration, though they all inhibited strongly at 10mm. 6. The oxidation of [1−14C]-myristate and -stearate, but not of [1−14C]decanoate, was strongly inhibited by 0·01mm-pent-4-enoic acid. 7. The oxidation of [1−14C]palmitate was about 50% carnitine-dependent under the experimental conditions used. 8. The percentage inhibition of [1−14C]palmitate oxidation by pent-4-enoic acid was the same whether carnitine was present or not. 9. Acetoacetate formation from saturated fatty acids was inhibited by 0·1mm-cyclopropanecarboxylic acid to a greater extent than their oxidation. 10. The other compounds tested inhibited acetoacetate formation from saturated fatty acids proportionately to the inhibition of oxidation. 11. Possible mechanisms for the inhibition of long-chain fatty acid oxidation by pent-4-enoic acid are discussed. 12. There was a correlation between the ability to inhibit long-chain fatty acid oxidation and hypoglycaemic activity in this series of compounds.
The effect of scurvy on glycosaminoglycans of granulation tissue and costal cartilage
Authors: Antonowicz I. , Kodicek E.
Published: August 2015

1. The effect of ascorbic acid deficiency on glycosaminoglycans of granulation tissue and cartilage of guinea pigs was investigated by determination of the changes in the glucosamine and galactosamine contents 12 days after tendonectomy. 2. In normal granulation tissue, the glucosamine and galactosamine contents rose to a peak at 5 and 10 days respectively, whereas the hydroxyproline and proline contents continued to rise throughout the 20 days after tendonectomy. 3. The galactosamine in scorbutic granulation tissue, but not in that of pair-fed controls, decreased significantly in absolute amount and relatively to glucosamine, which remained practically unchanged; the cartilage galactosamine did not decrease during the 22 days of deficiency owing to the presence of excess of preformed galactosaminoglycans, which masked the small amount of newly formed glycosaminoglycans. 4. The chemical results were confirmed by radioactivity studies in vivo of incorporation of [U−14C]glucose into galactosamine and glucosamine of scorbutic granulation tissue and cartilage. The incorporation of 14C into galactosamine decreased significantly in scurvy in both tissues. 5. The results indicated in both tissues a decreased formation of galactosamine during scurvy, although an increased degradation of polymerized glycosaminoglycans could not be entirely ruled out. It is concluded that, if lack of ascorbic acid causes an impaired galactosamine formation, the most likely position for the block may be in the UDP-N-acetylglucosamine 4-epimerase reaction.
Studies on the chromatin of barley leaves during senescence
Authors: Srivastava B. I. Sahai
Published: August 2015

1. The activity of soluble ribonuclease and deoxyribonuclease first declined during senescence, but later increased during advanced stages of senescence. 2. Young leaves had very low ribonuclease or deoxyribonuclease activity associated with the chromatin, but the activity of these enzymes increased progressively during senescence until the leaves died. 3. No significant changes in the composition of chromatin from first seedling leaves of barley plants during aging (from 7 to 25 days) were noted. 4. The amount of RNA synthesized by chromatin in vitro declined as the leaf aged. However, if the loss of RNA due to chromatin-associated ribonuclease was taken into account, the RNA-synthesizing activity of chromatin from senescing (15–16-day-old) leaves appeared to be somewhat higher than that of chromatin from young (7–8-day-old) leaves. In leaves at the terminal stages of senescence (23 days old) the estimates of RNA synthesis by chromatin could not be made owing to complications created by high nuclease activities. 5. It is suggested that senescence may be triggered by a decline in some hormonal factor in leaves, and that the resulting production of chromatin-associated deoxyribonuclease and ribonuclease in increasing proportions may progressively cause increased degradation of DNA and newly synthesized RNA, so that ultimately the cellular functions are impaired and the cells die.
Metabolic control mechanisms in mammalian systems. Hormonal regulation of phosphofructokinase in the rat prostate and seminal vesicles
Authors: Singhal Radhey L. , Valadares J. R. E.
Published: August 2015

1. The hormonal regulation of phosphofructokinase was investigated in the accessory reproductive organs of the orchidectomized rat. 2. Phosphofructokinase activities declined to 51% and 47% in the prostate and 9% and 6% of the normal values in seminal vesicles 4 and 8 weeks after castration respectively. Administration of testosterone (100μg./100g. body wt.) for 3 days reversed substantially the effects of orchidectomy, and phosphofructokinase activity increased to 173% in the prostate and 536% in seminal vesicles as compared with the values of castrated controls. 3. Time-course studies demonstrated that after a single injection of testosterone (5mg./100g. body wt.) phosphofructokinase activity was maximally elevated to 236% in the prostate and 342% in seminal vesicles at 24hr. 4. Dose–response studies revealed that 2·5mg. of testosterone propionate/100g. body wt. was the minimal amount necessary to induce significant increases in enzyme activity in both accessory sex organs; maximal increases were obtained with a dose of 5mg./100g. body wt. 5. The observed enzyme increases induced by testosterone were inhibited by the simultaneous administration of oestradiol-17β, and phosphofructokinase activity in this group of rats remained at 97% in the prostate and 137% of the control values in seminal vesicles. Oestradiol-17β by itself failed to produce any significant effect on enzyme activity in either of these secondary sexual tissues. 6. The nature of the testosterone-induced increases in phosphofructokinase activity was studied by using a variety of inhibitors of RNA and protein synthesis. Cycloheximide, 5-fluorouracil and ethionine largely blocked the androgen-stimulated rise in enzyme activity observed 24hr. after steroid injection. The inhibitory effect of ethionine was completely reversed by the simultaneous administration of methionine. 7. Actinomycin, which is known to inhibit the synthesis of messenger RNA as well as the synthesis of other cellular RNA fractions, when given simultaneously with the hormone, also inhibited the testosterone-induced increases in prostatic and seminal-vesicular phosphofructokinase. However, when the antibiotic was given 6 or 12hr. after injection of the steroid, practically no inhibition of phosphofructokinase induction was obtained. This indicates that, once the enzyme-forming machinery is turned on and allowed to operate for a few hours, actinomycin is incapable of reversing the hormone-induced enzyme responses. 8. The results presented suggest that new RNA and protein synthesis may be involved in the observed androgen-induced increases in phosphofructokinase activity in the prostate and seminal vesicles of the orchidectomized rat.
The metabolism of thymol by a Pseudomonas
Authors: Chamberlain Enid M. , Dagley S.
Published: August 2015

1. Pseudomonas putida when grown with thymol contained a meta-fission dioxygenase, which required ferrous ions and readily cleaved the benzene nucleus of catechols between adjacent carbon atoms bearing hydroxyl and isopropyl groups. 2. 3-Hydroxythymo-1,4-quinone was excreted towards the end of exponential growth and later was slowly metabolized. This compound was oxidized by partially purified extracts only when NADH was supplied; the substrate for the dioxygenase appeared to be 3-hydroxythymo-1,4-quinol, which was readily and non-enzymically oxidized to the quinone. 3. 2-Oxobutyrate (0·9 mole) was formed from 1 mole of 3-hydroxythymo-1,4-quinone with the consumption of 1 mole of oxygen; acetate, isobutyrate and 2-hydroxybutyrate (which arose from the enzymic reduction of 2-oxobutyrate) were also formed. 4. These products, which were produced only when the catechol substrate contained a third hydroxyl group, appeared to result from the enzymic hydrolysis of the ring-fission product.
Studies on the lipid content and phosphate requirement of glucose- and acetate-grown Escherichia coli
Authors: Damoglou A. P. , Dawes E A
Published: August 2015

1. The phosphate requirement, i.e. the concentration of inorganic orthophosphate that just ceases to be limiting for growth, of Escherichia coli N.C.T.C. 5928 was determined for growth in ammonium–salts media containing glucose or acetate as the carbon and energy source, and compared with that of six other strains of E. coli. 2. The phosphate requirement for E. coli N.C.T.C. 5928 growing on acetate was about ten times that for growth on glucose, but this difference was not observed with any of the other strains. 3. After about 40 generations' growth on acetate with phosphate limitation in a chemostat, the phosphate requirement of the cells gradually decreased until it was equivalent to that of the glucose-grown organism; a single passage through glucose batch culture sufficed to restore the original high phosphate requirement, indicating a permeability phenomenon. 4. The lipid content of E. coli N.C.T.C. 5928 grown on glucose or acetate was measured isotopically by fractionation of cells grown on inorganic [32P]orthophosphate and gravimetrically after extraction from the cells by three different methods; change of carbon source from glucose to acetate did not affect the lipid content, which remained constant at 8–9% of the bacterial dry weight.
Effect of nucleoside triphosphate and magnesium ion concentration on the stability and function of rat liver polysomes in vitro
Authors: Pronczuk A. W. , Baliga B. S. , Munro H. N.
Published: August 2015

The effects of different concentrations of ATP, GTP, UTP and CTP on polysome stability and function in a cell-free protein-synthesizing system prepared from rat liver were studied. Increasing the concentration of ATP in the incubation medium to 15mm resulted in progressive disaggregation of the polysomes; at ATP concentrations above 2mm their capacity to incorporate amino acids into peptide chains diminished. The same disaggregation phenomenon could be produced by incubating polysomes in a buffered medium containing 5mm-Mg2+ and increasing concentrations of ATP. Although the disaggregating action of ATP could be prevented by increasing Mg2+ concentration, the amino acid incorporation in the cell-free protein-synthesizing system remained impaired. The effects of different concentrations of GTP, UTP and CTP on polysome stability were similar to those of ATP. Increasing the concentrations of each nucleoside triphosphate also inhibited the hydrolysis of GTP in the cell-free protein-synthesizing system.
A further study on the dietary-regulated biosynthesis of high-sulphur wool proteins
Authors: Gillespie J. M. , Broad Andrea , Reis P. J.
Published: August 2015

When the diet of sheep is supplemented by the infusion of sulphur-containing amino acids or casein into the abomasum, the newly synthesized wool shows characteristic changes in its amino acid composition, with significant increases in cystine, proline and serine and decreases in aspartic acid and phenylalanine. This modification seems to be due entirely to an alteration in the overall composition of the high-sulphur proteins and to an increase in their proportion in the fibre. These variations are not the result of a change in the composition of individual proteins, but are due to alterations in their relative proportions and to the initiation of the synthesis of ‘new’ proteins, many of which are extremely rich in cystine. It is suggested that the heterogeneity of the high-sulphur proteins may be due, in part, to similar changes in composition caused by natural variations in the nutrition of sheep.
Further studies on phosphorylation and the thiol/disulphide ratio of histones in growth and development
Authors: Ord Margery G. , Stocken L A
Published: August 2015

1. The proportion of thiol groups in the total thiol+disulphide of histone extracts from fertilized eggs from Echinus and Psammechinus was increased during periods of structural alterations in the nucleus. 2. The probable start of DNA synthesis in the fertilized eggs coincided with periods of maximum thiol content. 3. Histone extracts from rat liver and regenerating liver were predominantly in the thiol form and no significant variations could be detected during the first 30hr. after partial hepatectomy. 4. An assay system was developed to follow the phosphorylation believed to be associated with the arginine-rich histone F3. Phosphorylation increased by 50% at 1 and 2hr. after partial hepatectomy. The phosphate content also increased during the period of DNA synthesis. 5. The increased phosphorylation found 1hr. after partial hepatectomy was not prevented by actinomycin or prior irradiation. 6. The phosphate content of histone F1 was very high in livers from foetal rats and declined in neonatal rats similarly to the decline in DNA synthesis.
Regulation of gluconeogenesis and lipogenesis. The regulation of mitochondrial pyruvate metabolism in guinea-pig liver synthesizing precursors for gluconeogenesis
Authors: Somberg Ethel W. , Mehlman Myron A.
Published: August 2015

1. The carboxylation of pyruvate to oxaloacetate by pyruvate carboxylase in guinea-pig liver mitochondria was determined by measuring the amount of 14C from H14CO3− fixed into organic acids in the presence of pyruvate, ATP, Mg2+ and Pi. The main products of pyruvate carboxylation were malate, fumarate and citrate. Pyruvate utilization, metabolite formation and incorporation of 14C from H14CO3− into these metabolites in the presence and the absence of ATP were examined. The synthesis of phosphoenolpyruvate from pyruvate and bicarbonate is minimal during continued oxidation of pyruvate. Larger amounts of phosphoenolpyruvate are formed from α-oxoglutarate than from pyruvate. Addition of glutamate, α-oxoglutarate or fumarate did not appreciably increase formation of phosphoenolpyruvate when pyruvate was used as substrate. With α-oxoglutarate as substrate addition of fumarate resulted in increased formation of phosphoenolpyruvate, whereas addition of succinate inhibited phosphoenolpyruvate formation. In the presence of added oxaloacetate guinea-pig liver mitochondria synthesized phosphoenolpyruvate in amount sufficiently high to play an appreciable role in gluconeogenesis. 2. Addition of fatty acids of increasing carbon chain length caused a strong inhibition of pyruvate oxidation and phosphoenolpyruvate formation, and greatly promoted carbon dioxide fixation and malate, citrate and acetoacetate accumulation. The incorporation of 14C from H14CO3−, [1−14C]pyruvate and [2−14C]pyruvate into organic acids formed was examined. 3. It is concluded that guinea-pig liver pyruvate carboxylase contributes significantly to gluconeogenesis and that fatty acids and metabolites play an important role in its regulation.
The effects of dietary conditions and glycerol concentration on glycerol uptake by rat liver and kidney-cortex slices
Authors: Robinson Janice , Newsholme E A
Published: August 2015

1. Glycerol utilization by rat liver and kidney-cortex slices was studied in an attempt to define factors that might be important in the regulation of glycerol utilization by these tissues in vivo; the formation of glucose from glycerol by kidney-cortex slices was also studied. 2. The rate of glycerol uptake by liver slices was not changed (in comparison with the normal fed control) by starvation (48hr.), feeding with a low-carbohydrate diet (4–8 days) or feeding with a diet containing 25% glycerol (up to 18 days). Similarly, starvation or a low-carbohydrate diet had no effect on uptake by kidney-cortex slices; however, feeding with the glycerol diet increased glycerol uptake by kidney-cortex slices. 3. The rates of glycerol uptake by slices from both tissues were increased on raising the glycerol concentration from 0·2mm to 2·5 or 5·0mm. 4. Starvation increased the conversion of glycerol into glucose by kidney-cortex slices, but there was no effect of the low-carbohydrate diet; the rate of glucose formation was increased by feeding with the 25%-glycerol diet and was proportional to the increase in glycerol uptake. The rate of glucose production by these slices was increased by raising the glycerol concentration in the incubation medium from 0·2mm to 1·0mm, but, except for the slices from animals receiving the 25%-glycerol diet, there was no effect above 1·0mm-glycerol. 5. The significance of plasma glycerol concentration in regulating glycerol uptake by these tissues is discussed.
A model for studying the initiation of normal calcification in vivo
Authors: Alcock Nancy W. , Reid Judith A.
Published: August 2015

1. Rat costal cartilage was found to begin to calcify normally when the rats weigh 35–45g. 2. The cartilage is suggested as a model for the study in vivo of mechanisms concerned with normal calcification. 3. The model was tested by studying the incorporation of fluoride into the mineral deposited in the tissue. 4. The percentage of inorganic material in cartilage rose from approx. 3% of the dry weight in the uncalcified tissue to 62% in the tissue from rats weighing 300g. 5. Mineral deposited had a calcium/phosphorus molar ratio of 1·65. 6. After the oral administration of sodium fluoride to rats, fluoride was incorporated into cartilage mineral. 7. The concentration of fluoride in cartilage ash increased rapidly with calcification and the mineral became more highly fluoridated than the corresponding rib bone. 8. Fluoridated mineral showed a marked decrease in citrate concentration.
Evidence for the presence of several lipases in cow's milk
Authors: Downey W K , Andrews P.
Published: August 2015

Skim milks containing sodium chloride (0·75m) were centrifuged at 80000g for 2hr. and portions of the supernatants were submitted to gel filtration on columns of Sephadex G-200. Enzymes in the effluent fractions were assayed titrimetrically for their hydrolytic activities towards tributyrin, triolein and milk-fat emulsions, and triacetin solution. Summation of the measurements gave ratios of activities towards the various substrates similar to those of the original skim milks. Although only partial separation was obtained, five enzymes appeared to be present. They showed some differences in substrate specificity, but all appeared to be lipases in that they hydrolysed the emulsified substrates more rapidly than the dissolved triacetin.
Temperature and the regulation of enzyme activity in poikilotherms. Properties of lungfish fructose diphosphatase
Authors: Behrisch Hans Werner , Hochachka Peter W.
Published: August 2015

1. The properties of fructose diphosphatase from liver of South American lungfish (Lepidosiren paradoxa) were examined. 2. Saturation curves for substrate (fructose diphosphate) and both cofactors (Mn2+ and Mg2+) are sigmoidal and Hill plots of these results suggest about 2 interacting substrate and cofactor sites/molecule of enzyme. 3. Mn2+ is an efficient positive modulator of the enzyme and Ka for Mn2+ is about 20–30-fold lower than the Ka for Mg2+. 4. Lungfish fructose diphosphatase is inhibited by low concentrations of AMP, and the affinity of the enzyme for AMP is insensitive to temperature. 5. The affinities of fructose diphosphatase for fructose diphosphate and Mn2+ appear to be dependent on temperature, whereas affinity for Mg2+ is temperature-independent. 6. The pH optimum of the enzyme depends on the presence of the particular cofactor. As pH increases, the Ka values of both cations are lowered, maximum velocities are increased and the saturation curves for cofactor become hyperbolic. 7. The possible roles of these ions, pH and substrate in the modulation of fructose diphosphatase and gluconeogenic activity in the lungfish are discussed in relation to aestivation and temperature adaptation.
o-Quinones formed in plant extracts. Their reaction with bovine serum albumin
Authors: Pierpoint W. S.
Published: August 2015

1. The reactions between chlorogenoquinone, the o-quinone formed during the oxidation of chlorogenic acid, and bovine serum albumin depend on the ratio of reactants. 2. When the serum albumin is in excess, oxygen is not absorbed and the products are colourless. This reaction probably involves the thiol group of bovine serum albumin; it does not occur with bovine serum albumin which has been treated with p-chloromercuribenzoate, iodoacetamide or Ellman's reagent. 3. When bovine serum albumin reacts with excess of chlorogenoquinone, oxygen is absorbed and the products are red. The red colour is probably formed by reaction of the lysine ∈-amino groups of bovine serum albumin, as it is prevented by treating the protein with formaldehyde, succinic anhydride or O-methylisourea. 4. Bovine serum albumin modified by a 1·5-fold (BSA-Q) and a fivefold (BSA-Q2) excess of chlorogenoquinone were separated by chromatography on DEAE-Sephadex A-50, and some of their properties observed. 5. Reaction of BSA-Q2 with fluorodinitrobenzene suggests that the terminal α-amino group, as well as lysine ∈-amino groups, are combined with chlorogenoquinone.
Methylmalonic acid and coenzyme A concentrations in the livers of pair-fed vitamin B12-deficient and vitamin B12-treated sheep
Authors: Smith R. M. , Osborne-White W. S. , Russell G. R.
Published: August 2015

The concentrations of CoA in the livers of severely vitamin B12-deficient ewes were about 2·6 times those in pair-fed animals treated with vitamin B12. When the feeding rates of the pair-fed animals were closely similar, the concentrations of methylmalonic acid in deficient livers were about twice those in vitamin B12-sufficient livers. The molar concentrations of CoA present were more than three times those of methylmalonic acid in both deficient and treated animals, and it is concluded that the elevated concentrations of CoA in the deficient livers were not primarily due to accumulation of methylmalonyl-CoA.
Analogues of ribose 5-phosphate and 5-phosphoribosyl pyrophosphate. The preparation and properties of ribose 5-phosphorothioate and 5-phosphoribosyl 1-methylenediphosphonate
Authors: Murray A. W. , Wong P. C. L. , Friedrichs Beverly
Published: August 2015

1. 5-Phosphoribosyl 1-methylenediphosphonate was isolated after reaction of ribose 5-phosphate and O-adenylyl methylenediphosphonate with 5-phosphoribosyl pyrophosphate synthetase from Ehrlich ascites-tumour cells. 2. The analogue reacted with adenine phosphoribosyltransferase, hypoxanthine phosphoribosyltransferase and nicotinamide phosphoribosyltransferase [Km (analogue)/Km (5-phosphoribosyl pyrophosphate) 0·17, 0·19 and 6·3 respectively; Vmax. (analogue)/Vmax. (5-phosphoribosyl pyrophosphate) 0·011, 0·26 and 1·1 respectively]. 3. The analogue was not a substrate for 5-phosphoribosyl pyrophosphate amidotransferase or orotate phosphoribosyltransferase. 4. Ribose 5-phosphorothioate was synthesized by allowing ribose to react with thiophosphoryl chloride in triethyl phosphate. The analogue was a substrate for 5-phosphoribosyl pyrophosphate synthetase from Ehrlich ascites-tumour cells. When this reaction was coupled to either adenine phosphoribosyltransferase or hypoxanthine phosphoribosyltransferase, adenosine 5′-phosphorothioate or inosine 5′-phosphorothioate was formed respectively.
Subunit structure of oyster paramyosin
Authors: Woods E. F.
Published: August 2015

Paramyosin from the oyster Crassostrea commercialis was studied by equilibrium sedimentation. In non-denaturing solvents the minimum molecular weight is 208000. Dissociation into subunits requires complete disruption of the α-helix. This occurs at pH7 in guanidine hydrochloride solutions of concentration greater than 7m in the presence of a disulphide-bond-reducing agent. Solutions of the protein in concentrated guanidine hydrochloride are polydisperse and contain species of low molecular weight (approx. 25000) comprising approx. 5% to 10% of the protein. The molecular weight of the main component is estimated to be 97000 and the paramyosin molecule contains two of these subunits. From the present observations no decision can be made as to whether or not the small component (or components) represents part of the paramyosin molecule. Preferential binding of guanidine hydrochloride to the extent of 0·13g./g. of protein was shown in solutions of paramyosin in 7·85m-guanidine hydrochloride.
An extracellular agarase from a Cytophaga species
Authors: Duckworth M , Turvey J R
Published: August 2015

1. An extracellular enzyme has been isolated from cultures of the bacterium growing on agar or porphyran. 2. Partial purification of the enzyme has been achieved by precipitation with ammonium sulphate followed by gel filtration on DEAE-Sephadex A-50. 3. The optimum conditions for the enzyme acting on porphyran are pH7·2 and a temperature of 40–41°. 4. The enzyme has an endoaction, producing a rapid decrease in viscosity of agar or porphyran solutions with little development of reducing power. 5. From the action of the enzyme on various polysaccharides, it is concluded that the enzyme is specific for the agarose structure.
The isolation, identification and synthesis of two metabolites of guanethidine formed in pig and rabbit liver homogenates
Authors: Abramson F. B. , Furst C. I. , McMartin C. , Wade Roy
Published: August 2015

1. Two metabolites of radioactively labelled guanethidine were isolated from rabbit and pig liver homogenates by ion-exchange chromatography on a sulphonic acid resin. 2. One of the metabolites was eluted from the column with ammonia and identified as 2-(6-carboxyhexylamino)ethylguanidine on the basis of the elemental analysis, i.r. spectrum and pH titration curve of the pure compound, and the observed partial loss of tritium for ring-labelled guanethidine during the formation of this metabolite. 3. This identification was confirmed by synthesis. 4. 2-(6-Carboxyhexylamino)ethylguanidine underwent ring-closure in hot alkaline solution to 1-(6-carboxyhexyl)-2-iminoimidazolidine. 5. The other metabolite of guanethidine was eluted from the ion-exchange column with 6m-hydrochloric acid along with the unchanged drug. It was purified by countercurrent distribution and shown to be identical with synthetic guanethidine N-oxide. 6. The two metabolites and the product of ring-closure had less than one-tenth of the antihypertensive activity of guanethidine in the renal-hypertensive rat and are unlikely to contribute to the pharmacological properties of the drug.
Increase in activity of glucose 6-phosphate dehydrogenase in mouse mammary tissue cultured with insulin
Authors: Leader D. P. , Barry J M
Published: August 2015

1. In organ cultures of mammary tissue from C3H mice we observed increases in the activity of glucose 6-phosphate dehydrogenase similar to that occurring at parturition. 2. In 22hr. cultures of tissue from late-pregnant mice insulin was required for the increases, but the further addition of prolactin, corticosterone and certain other hormones had no effect. The rise in activity occurred over the second half of the culture period. 3. Results from culture of adipose tissue, and mammary tissue rich in adipose tissue, strongly suggest that the rise in activity occurs in mammary parenchymal rather than adipose cells. 4. In 45hr. cultures prolactin prevented a fall in enzyme activity between 22hr. and 45hr. If the medium contained serum the activity at 22hr. was unaffected, but it continued to rise up to 45hr., and prolactin then had no effect. 5. The enzyme also increased in activity in cultures of mammary tissue from mid-pregnant mice. Insulin was again required, the activity was higher at 45hr. than at 24hr. and prolactin increased the activities at both these times. 6. Actinomycin D, cycloheximide and puromycin at low concentration in the media of 22hr. cultures all prevented increases in enzyme activity. Hydroxyurea at a concentration that inhibited the incorporation of [3H]thymidine into DNA by 92% had little effect. 7. Actinomycin D and cycloheximide largely failed to prevent the rise in enzyme activity if added after 3·5hr. and 12hr. respectively. Hence all essential RNA and protein synthesis appears to be finished by 3·5hr. and 12hr., although most of the increase in enzyme activity occurs gradually between 12hr. and 22hr. 8. We suggest that the increases in enzyme activity, both in culture and in the living animal at parturition, are induced by an influx of glucose that is restrained during pregnancy by the growth-hormone-like action of placental lactogen.
Teichoic acids possessing phosphate–sugar linkages in strains of Lactobacillus plantarum
Authors: Adams J. B. , Archibald A. R. , Baddiley J , Coapes Hilary E. , Davison A L
Published: August 2015

Cell walls of strains of Lactobacillus plantarum lacking the group D precipitinogen (a glucosylribitol teichoic acid) contain glucosylglycerol teichoic acid in which the glycosidic substituents are attached to the primary hydroxyl group of glycerol. Three distinct repeating units have been isolated from the teichoic acid preparation of strain C106, indicating either that the polymer is complex or that the wall contains a mixture of teichoic acids. Walls of streptobacteria differ from those of L. plantarum and contain neither teichoic acid nor diaminopimelic acid.
The pentose phosphate pathway of glucose metabolism. Influence of a growth-hormone-secreting pituitary tumour on the oxidative and non-oxidative reactions of the cycle in liver
Authors: Gumaa K. A. , MacLeod R. M. , McLean Patricia
Published: August 2015

1. Measurements were made of the activities of enzymes of the pentose phosphate cycle, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase, transketolase and transaldolase, as well as of the related or competing enzymes glucokinase, hexokinase, phosphoglucose isomerase and phosphoglucomutase, in control rats and in rats bearing the growth-hormone- and prolactin-secreting pituitary tumour MtTW5, to study the effect of high endogenous concentrations of growth hormone on this pathway in liver. 2. There was a twofold increase in liver weight. Glucokinase activity/g. of liver decreased to half the control value in the experimental group, although on a total liver basis it remained unchanged. Hexokinase activity increased in parallel with the liver weight, so that the total activity was doubled in rats with a high endogenous concentration of growth hormone. No differences in response were found between heat-stable and heat-labile forms of hexokinase. 3. The activity/g. of liver of the two oxidative enzymes of the pathway decreased slightly in the experimental group, but this was offset by the increase in liver weight, and the resultant effect was a 50% increase in the total activity. 4. Of the non-oxidative enzymes of the cycle the most marked increase on a total liver basis was in ribose 5-phosphate isomerase activity, to 2·5 times the control value. Ribulose 5-phosphate epimerase activity showed the smallest increase. Transketolase and transaldolase activities were also increased. The latter is the rate-limiting enzyme of the non-oxidative reactions of the cycle in these animals. 5. The results are discussed in relation to the glycolytic pathway and synthesis of glycogen, and more particularly to the increased requirement for ribose 5-phosphate for RNA synthesis.
Purification and properties of sheep liver phosphofructokinase
Authors: Brock D. J. H.
Published: August 2015

1. The activity of phosphofructokinase in sheep liver was found to be dependent on the composition and molarity of the buffer used in extraction. Under optimum conditions a value of 4–7μmoles/min./g. wet wt. of tissue was obtained. 2. The enzyme was purified 480-fold by a combination of ammonium sulphate fractionation, heat treatment in the presence of ethanol, DEAE-cellulose chromatography and Sephadex G-200 gel filtration. The final specific activity was 18·5μmoles/min./mg. of protein. 3. The purified enzyme was inhibited by ATP and citrate, the degree of inhibition depending on the concentration of fructose 6-phosphate, magnesium chloride and ammonium sulphate, as well as on the pH. ATP and citrate inhibition was overcome by AMP and fructose 1,6-diphosphate. 4. The enzyme was also inhibited by NADH and NADPH in a manner largely independent of other components of the assay medium. AMP and fructose 1,6-diphosphate were not able to overcome this type of inhibition. 5. Octanoate was not an inhibitor of phosphofructokinase. 6. Differences between these results and those of other workers are discussed.
The emission of corrosive vapours by wood. Hot - water - extracted O - acetylated hemicelluloses from sweet chestnut (Castanea sativa) and wych elm (Ulmus glabrau) and a discussion of O-acetyl-group changes occurring in these woods during incubation at 48° and 100% relative humidity
Authors: Cochrane G. C. , Gray J. D. , Arni P. C.
Published: August 2015

1. O-Acetylated polysaccharides were obtained from green wood of both sweet chestnut and wych elm by treatment of the residue remaining after dimethyl sulphoxide extraction with water at 98°. This gives a mixture of polysaccharides containing xylose, galactose, glucose and uronic acids. Analysis of these and their fractionated products suggest that only xylans in green sweet chestnut and green wych elm are O-acetylated. 2. The isolated O-acetylated xylans are not representative of the total O-acetylated xylans occurring in sweet chestnut and wych elm. 3. Application of the method developed by Bouveng for the location of O-acetyl groups to all four O-acetylated xylans obtained in this series of investigations by dimethyl sulphoxide extraction showed that those from sweet chestnut and wych elm, under the same conditions of incubation, lost: 74·2 and 43·4% of acetyl groups respectively, at C-2; 58·0 and 28·5% of acetyl groups respectively at C-3; 41·8 and 82·2% of acetyl groups respectively at C-2 and C-3. 4. A consideration of electronic and steric factors indicates that there does not appear to be a purely chemical reason for the difference in loss of O-acetyl groups between sweet chestnut and wych elm. It is suggested that the location of O-acetylated xylans in the wood cell walls and the presence of extractive may play some part in this difference.
The decomposition of soluble collagen by γ-irradiation
Authors: Cooper D. R. , Russell A. E.
Published: August 2015

1. The effect of γ-irradiation in the range 1 krad–10 Mrads on freeze-dried acid-soluble collagen was studied. 2. The specific-rotation and reduced-viscosity recoveries after heating and cooling of the irradiated collagen in solution showed a high degree of dependence on irradiation dose, with reduced viscosity showing significantly less recovery than specific rotation on increasing the irradiation dose. 3. The dependence of reduced viscosity on concentration was greatly decreased with increased doses of γ-irradiation. 4. The melting temperature measured by optical rotation also decreased as the irradiation dose was increased, and at low doses was distinctly biphasic. 5. Physical properties showed that the action of γ-irradiation up to 10 Mrads occurred in two distinct phases, with the early changes being extremely sensitive to irradiation dose. 6. The action of the γ-irradiation is discussed in terms of the structure of tropocollagen.
The inhibition of pepsin-catalysed reactions by products and product analogues. Kinetic evidence for ordered release of products
Authors: Greenwell P. , Knowles J. R. , Sharp Hilary
Published: August 2015

1. The inhibition of pepsin-catalysed hydrolysis of N-acetyl-l-phenylalanyl-l-phenylalanylglycine by products and product analogues was studied. 2. The non-competitive nature of the inhibition by the product N-acetyl-l-phenylalanine confirms an ordered release of products, and points to a common mechanism (involving an amino-enzyme) for pepsin-catalysed transpeptidation and hydrolysis reactions. 3. N-Acetyl-l-phenylalanine ethyl ester is also a non-competitive inhibitor, but here the inhibition is of the ‘dead-end’ type. No ethanol is detectable in reaction mixtures, indicating that this ester cannot act as an amino group acceptor in a transpeptidation process. 4. The same is true for N-methanesulphonyl-l-phenylalanine methyl and methyl thiol esters. No methanethiol is liberated when the methyl thiol ester is present as an inhibitor of the hydrolytic reaction, and the hope that such a thiol ester would effectively trap the amino-enzyme was not fulfilled.