bluuebunny/crossref_metadata_2025 huggingface dataset:
Intersubstrate competitions and evidence for compartmentation in mitochondria
Authors: Harris E J , Manger J R
Published: August 2015

1. The respiration of rat liver mitochondria was compared with different substrates, and with sucrose and saline media. The maximum rates of oxidation obtainable from glutamate, oxoglutarate, glutamate+malate, or succinate were higher in the saline (120mm)–tris (20mm) media than in sucrose (250mm)–tris (20mm) mixtures, but the rate with β-hydroxybutyrate was unchanged. Addition of valinomycin to a medium with sucrose and 5mm-potassium chloride led to rates similar to those measured in saline media; β-hydroxybutyrate oxidation was unaffected. 2. Some pairs of substrates together provided a rate of oxidation greater than the sum of the separate rates. This is accountable if removal of inhibitory products, such as oxaloacetate, compensates for any mutual competition between the substrates. Other pairs showed rates less than the sum of the separate rates, which is accountable by mutual competition. β-Hydroxybutyrate and other substrates, except succinate, provided strictly additive rates; with succinate there was evidence for competition. In the presence of rotenone, succinate oxidation was slowed down by citrate, oxoglutarate (+arsenite) and by β-hydroxybutyrate. 3. The accumulation of substrates in the mitochondria was measured as a function of the concentration and in the presence of possible competitors, or with a potassium salt and valinomycin to induce uptake of K+. The quantities of oxoglutarate, glutamate and pyruvate increased with the mitochondrial K+, but the quantities of β-hydroxybutyrate did not. Most substrates competed between themselves, although citrate accumulation was somewhat increased by oxoglutarate. β-Hydroxybutyrate competed for accumulation only with succinate, and was unaffected by other substrates. β-Hydroxybutyrate accumulation was almost linearly related to applied concentration (up to 5mm), and its rate of reaction was linearly dependent on concentration up to the highest value tested (0·75mm). Hence it differed from other substrates, which are accumulated and oxidized in a manner that follows a saturation law, with Km values about 1–10mm. 4. It is concluded that β-hydroxybutyrate is stored in a compartment operationally distinct from the space containing K+ and the NAD-linked substrates. It seems likely that succinate enters both compartments. 5. The degree of accumulation and the effectiveness of an anion as a competitor (as judged by low Ki) increases with the net charge. This is indicative of an electrostatic interaction with positive sites. It is suggested that the facilitating influence of dicarboxylic acids on the permeation of tricarboxylic acids may be due to the assembling of pairs of the positive carriers by the former, so favouring the chance of there being three or more carriers in a small volume of space near the boundary to interact with the tricarboxylic anion.
Studies on the origin of milk fat. A further study of bovine serum lipoproteins and an estimation of their contribution to milk fat
Authors: Bishop C. , Davies T. , Glascock R. F. , Welch V. A.
Published: August 2015

1. Tritium-labelled palmitic acid combined in olive-oil triglycerides was introduced into the rumen of a lactating cow and the specific radioactivity of the lipids of milk and of the lipoproteins of both jugular and mammary venous serum was measured. 2. As previously found in a similar experiment with [3H]stearic acid, the specific radioactivity of the triglyceride fraction of the dextran sulphate-precipitable lipoproteins reached a maximum earlier and greater than that of the milk fat. 3. This fraction was the only lipid separated that had a significant arteriovenous difference in concentration, and is therefore identified as the main circulating lipid precursor of milk fat. 4. Although the non-esterified fatty acids showed no arteriovenous difference in concentration, they showed a negative difference in specific radioactivity that could have occurred only at the expense of the triglycerides of the precipitable lipoproteins. 5. The mean specific radioactivity of the triglycerides immediately after removal from the blood is calculated and shown to be very close in value to that of the corresponding fraction in mammary venous serum. 6. By comparison of the mean specific radioactivities of milk fat and of this precursor, its contribution is calculated as 36%. 7. This value is discussed with reference to the concentration of C16 and C18 fatty acids in milk fat and it is concluded that substantial amounts of these acids must have been derived from a source other than preformed circulating lipids.
The effect of protein content of the diet on the rate of urea formation in sheep liver
Authors: Payne E. , Morris J G
Published: August 2015

1. In the livers of six sheep given a high-protein diet, the concentrations of certain urea-cycle enzymes [ornithine transcarbamoylase, arginine synthetase (combined activity of argininosuccinate synthetase and argininosuccinase) and arginase] were significantly greater than when the sheep were given a low-protein diet. Alkaline phosphatase activity/mg. of liver protein was not significantly affected by diet. 2. Three sheep previously given the high-protein diet showed no significant rise in the concentration of ammonia in the blood after the administration of urea (0·5g./kg. body wt.). The concentration of ammonia in the blood of the three sheep given the low-protein diet rose exponentially with time after dosing with urea and all sheep died. 3. It is suggested that tolerance to ammonia toxicity in the sheep is at least partly a function of the activity of the urea-cycle enzymes in the liver.
The subunit structure of jack-bean urease
Authors: Bailey C. J. , Boulter D.
Published: August 2015

1. Urease of specific activity 160–180 Sumner units/g. (Sumner, 1951) was purified from jack-bean meal. The preparation was pure on the basis of polyacryl-amide-gel electrophoresis and N-terminal studies. 2. By using both the 1-fluoro-2,4-dinitrobenzene method and the phenyl isothiocyanate method a single N-terminal methionine residue was found. 3. A single C-terminal sequence -Tyr-Leu-Phe was found by studies with carboxypeptidase A, carboxypeptidase B and hydrazinolysis. 4. N-Bromosuccinimide cleavage showed that five unique tryptophan sequences were present: Trp-Ala, Trp-Glu, Trp-Gly, Trp-Met and Trp-Arg. 5. Polyacrylamide-gel electrophoresis in sodium dodecyl sulphate showed that urease had a subunit molecular weight of 76000. 6. The yield of N- and C-terminal amino acids, the number of tryptic peptides and tryptophan sequences and the above polyacrylamide-gel electrophoretic measurement all suggest that urease contains a single structural subunit of molecular weight 75000.
Changes in certain kinetic properties of hepatic microsomal aniline hydroxylase and ethylmorphine demethylase associated with postnatal development and maturation in male rats
Authors: Gram Theodore E. , Guarino Anthony M. , Schroeder David H. , Gillette James R.
Published: August 2015

1. Changes in certain kinetic properties (Vmax. and apparent Km) of hepatic microsomal mixed-function oxidases have been studied as a function of postnatal development and maturation in male rats. 2. Microsomal cytochrome P-450 content changed only slightly between 1 and 12 weeks of age. 3. Aniline hydroxylase activity (Vmax.) increased abruptly between 1 and 2 weeks of age to greater than adult activities and then returned to a plateau value between 4½ and 12 weeks of age. Ethylmorphine demethylase activity remained low and relatively constant between 1 and 3 weeks of age and then increased markedly (∼100%) between 3 and 4½ weeks. 4. The apparent Michaelis constant (Km) for aniline hydroxylation increased almost linearly with time between 1 and 6 weeks of age and tended to reach a plateau value thereafter. The apparent Km for ethylmorphine demethylation increased between 1 and 3 weeks of age and then decreased abruptly to a constant value between 6 and 12 weeks. 5. The data indicate that developmental changes in the activity of these microsomal oxidases do not correlate temporally with each other or with changes in microsomal cytochrome P-450 content. 6. The most dramatic changes in enzyme activity were associated with early development (1–3 weeks) and weaning (3–4 weeks). 7. Changes in weight of seminal vesicle, a criterion of sexual maturation in male rats, were most prominent between 6 and 8 weeks of age and thus appeared to be separated in time from the prominent changes in enzyme activity.
The specificity of an agarase from a Cytophaga species
Authors: Duckworth M , Turvey J R
Published: August 2015

1. The extracellular agarase from a Cytophaga species was shown to have no action on neoagarobiose, neoagarotetraose or their analogues containing 6-O-methyl-d-galactose residues. 2. The action of the enzyme on neoagaro-octaose suggests that scission of the central β-d-galactosidic linkage, to form two molecules of tetrasaccharide, is the preferred mode of action; however, both exterior d-galactosidic linkages in the octasaccharide and both in neoagarohexaose are hydrolysed at a somewhat lower rate. 3. Sulphated oligosaccharides produced by prolonged enzyme action on porphyran have a minimum degree of polymerization of about 8–10units. 4. For such sulphated oligosaccharides to be further hydrolysed by enzyme action, it is suggested that an unmodified neoagarotetraose residue must be present in the oligosaccharide. 6. A new method for determining the degree of polymerization of these large oligosaccharides is described.
Selective effect of hormones on nucleic acid metabolism during germination of pear embryos
Authors: Khan A. A. , Heit C. E.
Published: August 2015

1. The effect of hormones on 32P incorporation into various RNA fractions in germinating pear embryos was studied by fractionation on methylated albumin–kieselguhr columns. Abscisic acid inhibited labelling of soluble RNA, DNA–RNA hybrid and light-ribosomal RNA fractions with 32P and this effect was reversed by both kinetin and gibberellic acid. 2. Kinetin reversed the inhibition by abscisic acid of 32P incorporation into total ribosomal RNA and appeared to promote labelling of heavy-ribosomal RNA. Gibberellic acid was more active than kinetin in reversing the inhibition by abscisic acid of labelling of the DNA–RNA hybrid fraction with 32P, but in contrast with kinetin appeared to increase further the inhibition by abscisic acid of labelling of total ribosomal RNA. 3. The percentage of radioactivity in various RNA fractions showed marked variation in response to hormones. 4. The pattern of labelling of RNA in pear embryos during reversal of inhibition by abscisic acid with a combination of kinetin and gibberellic acid was similar to that after cold-treatment of dormant pear embryos. This is suggestive of hormonal interplay in dormancy release by cold-treatment in pear embryos.
Acetylation of serotonin in vitro by a human N-acetyltransferase
Authors: White Thomas A. , Jenne John W. , Evans David A. Price
Published: August 2015

1. There is a well-recognized genetic polymorphism for the N-acetylation of isoniazid and sulphamethazine by human livers. 2. Serotonin was found to be acetylated by human liver enzyme preparations and the N-acetylserotonin formed was identified and determined quantitatively. 3. In 13 livers examined there was a wide variability in the capacity to acetylate serotonin that did not correlate with the capacity of the same livers to acetylate isoniazid and sulphamethazine. The results suggest that serotonin is not a natural substrate for the polymorphic N-acetyltransferase and that it may be acetylated by a different enzyme.
The separation and distribution of simple and condensed leucoanthocyanins of the tea plant (Camellia sinensis L.)
Authors: Forrest G. I. , Bendall D S
Published: August 2015

1. Leucoanthocyanin monomers of high mobilities in aqueous solvents on thinlayer chromatograms, assumed to be structurally simple, were characteristic of mature bulky tissues, whereas members of lower mobility were confined to young vegetative and floral tissues. 2. Flavylogens were separated by gel filtration on Sephadex columns into monomeric, oligomeric and polymeric fractions. 3. The polymeric fraction from young brown stems was heterogeneous, one-half having a molecular weight of about 3400, one-third a molecular weight between 3600 and 17000, and the remainder a molecular weight of over 17000. 4. Leaves had low flavylogen concentrations; only monomers were present. Stem tissues were rich in polymers, which increased with the age of the young stem and decreased inwards through the wood. The maximal flavylogen concentrations were in the phloem and cambium from mature stems, where all three fractions were richly present. The periderm tissue and, to a lesser extent, the seed coat were characterized by a very high polymer/monomer ratio, exhibiting a much higher degree of polymerization than the wood. Root tissues contained high concentrations of monomers. 5. In general, there was an inverse correlation between the extent of polymerization and the complexity of the monomers present. 6. The results are in favour of the thesis that the function of the flavanols is, after polymerization to condensed tannins, to impregnate dead structural tissues and thereby to protect them from infection and decay.
The effects of pH and citrate on the activity of nicotinamide–adenine dinucleotide-specific isocitrate dehydrogenase from pea mitochondria
Authors: Cox G. F. , Davies D. D.
Published: August 2015

1. The effect of pH on the co-operative activation of the NAD-specific isocitrate dehydrogenase from pea mitochondria by isocitrate is shown. 2. The interlinked effects of pH on the affinity of the NAD-specific isocitrate dehydrogenase for isocitrate and the dependence of the pH optimum on the substrate concentration are presented. 3. A consideration of the conditions of pH and substrate concentration under which citrate activates the NAD-specific isocitrate dehydrogenase demonstrates similarities between the binding of isocitrate and citrate. 4. A comparison of the effects of citrate and pH on the gross structure of the enzyme is investigated by density-gradient centrifugation. 5. The kinetic interpretations of these results are briefly considered. 6. The metabolic significance of these studies is discussed.
Studies on protein–polysaccharides from pig laryngeal cartilage. Extraction and purification
Authors: Tsiganos C. P. , Muir Helen
Published: August 2015

1. Protein–polysaccharides of chondroitin sulphate were extracted from fresh laryngeal cartilage at pH6·8 by two procedures. Procedure I consisted of brief low-speed homogenization in 0·15m (iso-osmotic) sodium acetate and procedure II consisted of longer homogenization followed by prolonged extraction in 10% calcium chloride solution. 2. The protein–polysaccharides in both extracts were isolated and purified by precipitation with 9-aminoacridine hydrochloride. They were free from serum proteins, collagen and nucleic acids and also of degradative enzymes. The absence of such enzymes was shown by viscosity measurements on solutions of protein–polysaccharides incubated for up to 24hr. at pH4 and 6·8. 3. Mannose, glucose or fucose were not detected by paper chromatography and only traces of sialic acid were present. 4. The yield with procedure II was twice that with procedure I and the products differed in their protein and glucosamine contents. 5. Hyaluronic acid was unlikely to have been precipitated at an acid pH, so the glucosamine was attributed to keratan sulphate, as serum proteins were absent. There was no free keratan sulphate in the preparation. 6. Both preparations were heterogeneous in the ultracentrifuge, showing at least three components.
Gentisic acid and its 3- and 4-methyl-substituted homologues as intermediates in the bacterial degradation of m-cresol, 3,5-xylenol and 2,5-xylenol
Authors: Hopper D. J. , Chapman P. J.
Published: August 2015

1. Intact cells of a non-fluorescent Pseudomonas grown with m-cresol, 2,5-xylenol, 3,5-xylenol, 3-ethyl-5-methylphenol or 2,3,5-trimethylphenol rapidly oxidized all these phenols to completion. 3-Hydroxybenzoate and 2,5-dihydroxybenzoate (gentisate) were also readily oxidized. 2. 3-Hydroxybenzoic acid and 2,5-dihydroxybenzoic acid were isolated as products of m-cresol oxidation by cells inhibited by αα′-bipyridyl. Alkyl-substituted 3-hydroxybenzoic acids and alkyl-substituted gentisic acids were formed similarly from 2,5-xylenol, 3,5-xylenol, 3-ethyl-5-methylphenol and 2,3,5-trimethylphenol. 3. When supplemented with NADH, not NADPH, extracts of cells grown with 2,5-xylenol catalysed the oxidation of all five phenols and accumulated the corresponding gentisic acids in the presence of αα′-bipyridyl. 4. Cells of a fluorescent Pseudomonas grown with m-cresol oxidized m-cresol, 3,5-xylenol and 3-ethyl-5-methylphenol to completion and oxidized 2,5-xylenol and 2,3,5-trimethylphenol partially. The oxidation product of 2,5-xylenol was identified as 3-hydroxy-4-methylbenzoic acid. In the presence of αα′-bipyridyl, 3-hydroxy-5-methylbenzoic acid and 3-methylgentisic acid were formed from 3,5-xylenol.
An improved procedure for the isolation of 3-phosphoglycerate kinase from yeast
Authors: Scopes R. K.
Published: August 2015

3-Phosphoglycerate kinase has been isolated from yeast by a new procedure. Over 1g was obtained from 450g of granulated baker's yeast; it had a specific activity of up to 940units/mg at 30°C. Six distinct crystalline forms have been grown, at least one of these being suitable for X-ray diffraction studies. The crystalline preparation is pure, judged by starch-gel or sodium dodecyl sulphate–polyacrylamide-gel electrophoresis; the latter method indicating that the enzyme is monomeric, with a molecular weight near to 50000.
The subunits of chemically treated proteoglycan isolated from bovine nasal cartilage
Authors: Serafini-Fracassini A. , Stimson W. H. , Floreani L.
Published: August 2015

1. The light fraction of the proteoglycan of bovine nasal cartilage was split by treatment with 0.1m-hydrochloric acid in acetone. The products were separated by gel filtration on 4% agarose and two retarded fractions were detected and isolated. These two fractions were found to have a Stokes radius of 134 and 47 Å respectively, as determined by calibration of the column against proteins of known hydrodynamic volumes. 2. The 47 Å fraction had a protein content of 4% and a glucosamine/galactosamine ratio 1:23. The 134 Å fraction had a protein content of 20% and a glucosamine/galactosamine ratio 1:4.8. 3. The results of the viscometric studies on both fractions suggested that the 134 Å fraction alone exhibited the property of undergoing reversible pH-dependent aggregation with a transition point at pH4.9. 4. It was concluded that these fractions could represent subunits of the native cartilage proteoglycan.
The isotope-exchange reactions of ox heart phosphofructokinase
Authors: Hulme E. C. , Tipton K. F.
Published: August 2015

1. Ox heart phosphofructokinase catalyses isotope-exchange reactions at pH6.7 between ADP and ATP, and between fructose 6-phosphate and fructose 1,6-diphosphate, the latter reaction being absolutely dependent on the presence of the magnesium complex of ADP. 2. The reaction kinetics are hyperbolic with respect to substrate concentration for both exchange reactions (within the experimental error). 3. The influence of pH, AMP and citrate suggests that the fructose 6-phosphate–fructose 1,6-diphosphate exchange is subject to effector control, and is abolished by dissociation of the enzyme. 4. These results are discussed in relation to the reaction mechanism of the enzyme.
Accumulation of untranslated lactose-specific messenger ribonucleic acid during catabolite repression in Escherichia coli
Authors: Aboud M. , Burger M.
Published: August 2015

When Escherichia coli K-12 Hfr.H was induced to synthesize β-galactosidase in the presence of glucose, an untranslated lactose-specific mRNA (lac-mRNA), protected from decay, was found to accumulate progressively within the cells. The lac-mRNA accumulation was unaffected by the carbon source on which the cells had been grown before the induction. The amount of the lac-mRNA available for translation was affected by catabolite repression and 3′:5′-cyclic AMP, but it remained unclear whether this was a direct effect on the formation of the lac-mRNA or a consequence of the effect on its translation.
Kinetics and mechanisms of catalase in peroxisomes of the mitochondrial fraction
Authors: Chance B. , Oshino N.
Published: August 2015

1. The primary intermediate of catalase and hydrogen peroxide was identified and investigated in peroxisome-rich mitochondrial fractions of rat liver. On the basis of kinetic constants determined in vitro, it is possible to calculate with reasonable precision the molecular statistics of catalase action in the peroxisomes. 2. The endogenous hydrogen peroxide generation is adequate to sustain a concentration of the catalase intermediate (pm/e) of 60–70% of the hydrogen peroxide saturation value. Total amount of catalase corresponds to 0.12–0.15nmol of haem iron/mg of protein. In State 1 the rate of hydrogen peroxide generation corresponds to 0.9nmol/min per mg of protein or 5′ of the mitochondrial respiratory rate in State 4. 3. Partial saturation of the catalase intermediate with hydrogen peroxide (pm/e) in the mitochondrial fraction suggests its significant peroxidatic activity towards its endogenous hydrogen donor. A variation of this value (pm/e) from 0.3 in State 4 to 0 under anaerobic conditions is observed. 4. For a particular preparation the hydrogen peroxide generation rate in the substrate-supplemented State 4 corresponds to 0.17s-1 (eqn. 6), the hydrogen peroxide concentration to 2.5nm and the hydrogen-donor concentration (in terms of ethanol) to 0.12mm. The reaction is 70% peroxidatic and 30′ catalatic. 5. A co-ordinated production of both oxidizing and reducing substrates for catalase in the mitochondrial fraction is suggested by a 2.2-fold increase of hydrogen peroxide generation and a threefold increase in hydrogen-donor generation in the State 1 to State 4 transition. 6. Additional hydrogen peroxide generation provided by the urate oxidase system of peroxisomes (8–12nmol of uric acid oxidized/min per mg of protein) permits saturation of the catalase with hydrogen peroxide to haem occupancy of 40′ compared with values of 36′ for a purified rat liver catalase ofk1=1.7×107m-1·s-1 and k′4=2.6×107m-1· s-1(Chance, Greenstein & Roughton, 1952). 7. The turnover of the catalase ethyl hydrogen peroxide intermediate (k′3) in the peroxisomes is initially very rapid since endogenous hydrogen peroxide acts as a hydrogen donor. k′3 decreases fivefold in the uncoupled state of the mitochondria.
Studies on metabolism of vitamin A. The effect of vitamin A status on the secretion rates of some steroids into the ovarianvenous blood of pregnant rats
Authors: Ganguly J. , Pope G. S. , Thompson S. Y. , Toothill Joyce , Edwards-Webb J. D. , Waynforth H. B.
Published: August 2015

1. Rats raised on a vitamin A-deficient diet supplemented with either retinyl acetate or retinoic acid were mated and became pregnant. 2. The rates of secretion of progesterone, 20α-hydroxypregn-4-en-3-one, oestradiol-17β and oestrone into the ovarian-venous blood of rats in these two groups were measured on days 9 and 15 of pregnancy. 3. Rates of secretion of progesterone and 20α-hydroxypregn-4-en-3-one, both on days 9 and 15, were lower for the rats given retinoic acid. No such differences were found in ovarian oestrogen secretion. 4. The implications of these results are discussed in the light of the previous demonstration that the activity of ovarian 3β-hydroxy-Δ5-steroid dehydrogenase was markedly less in pregnant rats given retinoic acid.
The purification and properties of microsomal palmitoyl-coenzyme A synthetase
Authors: Bar–Tana J. , Rose G. , Shapiro B.
Published: August 2015

The isolation and purification of palmitoyl-CoA synthetase from rat liver microsomes is described. Several methods suitable for enzyme assay are described. The general properties and kinetic parameters of the purified enzyme were determined and are discussed in relationship to microsomal fatty acid activation.
Relationship between alkaline phosphatase and neomycin formation in Streptomyces fradiae
Authors: Majumdar Mrinal K. , Majumdar S. K.
Published: August 2015

Studies on phosphatase activity of Streptomyces fradiae 3535 grown in three different media indicate that neomycin formation varies directly with enzyme activity, sodium nitrate–maltose–mineral salts medium giving the highest yields of alkaline phosphatase and neomycin. S. fradiae contains more than one alkaline phosphatase and the phosphatase responsible for hydrolysis of neomycin phosphate appears to be substrate specific. The same enzyme apparently hydrolyses both the N–P and P–O–P bonds of neomycin pyrophosphate. The enzyme is stimulated by Ca2+, is inactive at a pH below 7 and is inhibited by EDTA. Enzymic activity increases when mycelia are incubated in mineral salts medium, but decreases when phosphate or glucose is included in the medium, although the latter is more effective. The inhibitory effect of EDTA on neomycin formation by resting mycelia is completely reversed by Ca2+.
Isolation of normal immunoglobulin E by means of an immunoadsorbent
Authors: Carrel S. , Theilkäs Lore , Morell A. , Skvaril F. , Barandun S.
Published: August 2015

An improved method for the isolation of normal immunoglobulin E is described. The method is based on the use of an immunoadsorbent formed by the mechanical entrapment of antibodies against a myeloma immunoglobulin E into a lattice of a highly cross-linked macroporous polyacrylamide gel. Normal immunoglobulin E was isolated from an immunoglobulin E-rich serum pool as well as from an individual healthy donor. The isolated immunoglobulin E was contaminated with about 20% of immunoglobulin G. An antiserum against normal immunoglobulin E was prepared by immunizing rabbits with the isolated immunoglobulin E.
The substrate specificity of purine phosphoribosyltransferases in Schizosaccharomyces pombe
Authors: De Groodt A. , Whitehead E. P. , Heslot H. , Poirier L.
Published: August 2015

1. The activities of the purine phosphoribosyltransferases (EC 2.4.2.7 and 2.4.2.8) in purine-analogue-resistant mutants of Schizosaccharomyces pombe were checked. An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. Two 2,6-diaminopurine-resistant mutants retained these activities but lacked adenine phosphoribosyltransferase activity (EC 2.4.2.7). This evidence, together with data on purification and heat-inactivation patterns of phosphoribosyltransferase activities towards the various purines, strongly suggests that there are two phosphoribosyltransferase enzymes for purine bases in Schiz. pombe, one active with adenine, the other with hypoxanthine, xanthine and guanine. 2. Neither growth-medium supplements of purines nor mutations on genes involved in the pathway for new biosynthesis of purine have any influence on the amount of hypoxanthine–xanthine–guanine phosphoribosyltransferase produced by this organism.
Proteins of normal hair and of cysteine-deficient hair from mentally retarded siblings
Authors: Pollitt R. J. , Stonier P. D.
Published: August 2015

1. S-Carboxymethylkerateines extracted from normal hair can be fractionated into high-sulphur and low-sulphur proteins similar to those obtained from sheep's wool. Normal human hair gives a major high-sulphur protein of higher molecular weight and S-carboxymethylcysteine content than any isolated from normal sheep's wool. 2. The proteins from cystine-deficient hair can also be divided into high-sulphur and low-sulphur proteins. There is a lower proportion of high-sulphur protein in cystine-deficient hair than in normal hair. 3. The high-sulphur proteins from cystine-deficient hair have an abnormal amino acid composition and in particular are lower in S-carboxymethylcysteine content than the corresponding proteins from normal hair. New components are present and the content of very high-sulphur proteins of high molecular weight is much decreased. The low-sulphur proteins of cystine-deficient hair are probably also deficient in S-carboxymethylcysteine. 4. The proteins of cystine-deficient hair probably resemble those in the normal hair root, except that disulphide-bridge formation has occurred.
The amino acid sequences of erabutoxins, neurotoxic proteins of sea-snake (Laticauda semifasciata) venom
Authors: Sato S. , Tamiya N.
Published: August 2015

1. Erabutoxin b was reduced, S-carboxymethylated and hydrolysed with trypsin. Seven tryptic fragments were isolated by column chromatography and paper electrophoresis. Some of the fragments were further hydrolysed with α-chymotrypsin, pepsin, Nagarse, Proctase A or Proctase B. The amino acid sequences of the fragment peptides were determined by subtractive Edman degradation. 2. From the tryptic digest of reduced, S-carboxymethylated and trifluoroacetylated erabutoxin b two fragments were isolated. From the amino acid composition of the fragments and from the terminal sequence studies on the reduced and S-carboxymethylated erabutoxin b, the sequence of the above seven tryptic fragments was elucidated. 3. The tryptic digestion of reduced and S-carboxymethylated erabutoxin a gave fragments, only one of which was different from the corresponding fragment from erabutoxin b. The amino acid sequence analysis of the fragment peptide showed that the only difference between erabutoxins a and b was that the former had asparagine and the latter had histidine at position 26.
Metabolism of 4-chloro-2-methylphenoxyacetate by a soil pseudomonad. Ring-fission, lactonizing and delactonizing enzymes
Authors: Gaunt J. K. , Evans W. C.
Published: August 2015

1. A cell-free system, prepared from Pseudomonas N.C.I.B. 9340 grown on 4-chloro-2-methylphenoxyacetate (MCPA) was shown to catalyse the reaction sequence: 5-chloro-3-methylcatechol → cis–cis-γ-chloro-α-methylmuconate → γ-carboxymethylene-α-methyl-Δαβ-butenolide → γ-hydroxy-α-methylmuconate. 2. The activity of the three enzymes involved in these reactions was completely resolved and the lactonizing and delactonizing enzymes were separated. 3. This part of the metabolic pathway of 4-chloro-2-methylphenoxyacetate is thus confirmed for this bacterium. 4. The ring-fission oxygenase required Fe2+ or Fe3+ and reduced glutathione for activity; the lactonizing enzyme is stimulated by Mn2+, Mg2+, Co2+ and Fe2+; no cofactor requirement could be demonstrated for the delactonizing enzyme. 5. cis–cis-γ-Chloro-α-methylmuconic acid was isolated and found to be somewhat unstable, readily lactonizing to γ-carboxymethylene-α-methyl-Δαβ-butenolide. 6. Enzymically the lactonization appears to be a single-step dehydrochlorinase reaction.
Bacterial metabolism of 2,4-dichlorophenoxyacetate
Authors: Evans W. C. , Smith B. S. W. , Fernley H. N. , Davies J. I.
Published: August 2015

1. Two Pseudomonas strains isolated from soil metabolized 2,4-dichlorophenoxyacetate (2,4-D) as sole carbon source in mineral salts liquid medium. 2. 2,4-Dichlorophenoxyacetate cultures of Pseudomonas I (Smith, 1954) contained 2,4-dichlorophenol, 2-chlorophenol, 3,5-dichlorocatechol and α-chloromuconate, the last as a major metabolite. 3. Dechlorination at the 4(p)-position of the aromatic ring must therefore take place at some stages before ring fission. 4. Pseudomonas N.C.I.B. 9340 (Gaunt, 1962) cultures metabolizing 2,4-dichlorophenoxyacetate contained 2,4-dichloro-6-hydroxyphenoxyacetate, 2,4-dichlorophenol, 3,5-dichlorocatechol and an unstable compound, probably αγ-dichloromuconate. 5. Cell-free extracts of the latter organism grown in 2,4-dichlorophenoxyacetate cultures contained an oxygenase that converted 3,5-dichlorocatechol into αγ-dichloromuconate, a chlorolactonase that in the presence of Mn2+ ions converted the dichloromuconate into γ-carboxymethylene-α-chloro-Δαβ-butenolide, and a delactonizing enzyme that gave α-chloromaleylacetate from this lactone. 6. Pathways of metabolism of 2,4-dichlorophenoxyacetate are discussed.
Synthesis and oxidation of aminoalkyl-onium compounds by pig kidney diamine oxidase
Authors: Bardsley W. G. , Ashford J. S. , Hill C. M.
Published: August 2015

1. The preparation of a series of compounds derived from diamines by replacing one amino group by a dimethylsulphonium, isothiuronium, trimethylammonium, NN′-dimethylimidazolium or N-methylpyridinium species is described. 2. The behaviour of these compounds as substrates of pig kidney diamine oxidase is reported. All but the trimethylammonium compounds proved to be substrates. 3. Many of these compounds showed potent inhibition at high substrate concentration and this was studied. 4. On the basis of these and other observations a scheme for enzyme–substrate interaction is suggested.
A requirement for dietary lipids for induction of cytochrome P-450 by phenobarbitone in rat liver microsomal fraction
Authors: Marshall W. J. , McLean A. E. M.
Published: August 2015

1. Rats fed on purified synthetic diets have a markedly lower cytochrome P-450 concentration and hydroxylating enzyme activity in liver microsomal fraction than rats fed on stock pellets. 2. When both groups are treated with phenobarbitone the difference is even greater, the purified diet allowing only 50% of the cytochrome P-450 concentrations of controls. 3. Addition of herring oil, linoleic acid or 0.1% oxidized sitosterol to the diets allows induction of cytochrome P-450 to take place. 4. Addition of coconut oil to the diet does not permit induction of cytochrome P-450. 5. The interactions between dietary protein and the lipid substances are explored. 6. The mechanism of induction of microsomal hydroxylation enzymes by drugs is discussed in the light of these requirements.
Studies on the accessibility of deoxyribonucleic acid in deoxyribonucleoprotein to cationic molecules
Authors: Itzhaki Ruth F.
Published: August 2015

The binding of deoxyribonucleoprotein to Toluidine Blue, to cetylpyridinium chloride and to polylysine of various molecular weights was studied to determine the percentage of free DNA phosphate groups in deoxyribonucleoprotein. Binding was measured by addition of these reagents to deoxyribonucleoprotein at a range of concentrations such that complete precipitation of the deoxyribonucleoprotein occurred. With Toluidine Blue the binding corresponded to about 48% of the DNA phosphates in deoxyribonucleoprotein. The dye did not cause appreciable displacement of protein from the DNA. With cetylpyridinium chloride the binding corresponded to about 41% of the DNA phosphates. With polylysine preparations of molecular weight 1250 and 7790 the binding values for deoxyribonucleoprotein were 46 and 38% respectively. The results suggest that the free phosphates lie in stretches sufficiently long to accommodate most of each polylysine molecule. With polylysine of molecular weight 62000 cross-linking of free stretches of DNA on different deoxyribonucleoprotein molecules probably occurs. It is concluded that although most of the free phosphates are probably ‘hidden’ beneath covering histone, corresponding perhaps to runs of non-basic residues in the latter, they are surprisingly accessible to very large molecules. The relevance of this finding to the problem of gene repression is discussed.
Rabbit Tamm–Horsfall urinary glycoprotein. Chemical composition and subunit structure
Authors: Marr Anne M. S. , Neuberger A. , Ratcliffe Wendy A.
Published: August 2015

1. Tamm–Horsfall glycoprotein from rabbit urine has been isolated and characterized. The homogeneity of the preparation has been established by a variety of procedures including disc gel electrophoresis and ultracentrifugation in aqueous solution, sodium dodecyl sulphate and formic acid. 2. The chemical composition has been determined and a carbohydrate content of approx. 31% was obtained. The relative contents of the amino acids were shown to be very similar to those in human Tamm–Horsfall glycoprotein. A trace of lipid was also detected. 3. Leucine was identified as the only N-terminal amino acid. 4. The subunit structure was investigated in the presence of sodium dodecyl sulphate by gel filtration and disc gel electrophoresis. These studies indicated that the subunit possessed a molecular weight of approx. 84000±6000. A similar value was obtained after reduction and S-alkylation of the glycoprotein indicating that the disulphide bonds were all intrachain. 5. A minimum value for the chemical molecular weight of 85000±6000 was obtained from the number of N-terminal amino acids released by cyanogen bromide cleavage of the glycoprotein. 6. The immunological properties of the glycoprotein were studied. Cross reactivity was demonstrated between human Tamm–Horsfall glycoprotein and a guinea-pig anti-rabbit Tamm–Horsfall antiserum.
Metabolic effects of the major component of bovine growth hormone
Authors: Swislocki N. I. , Sonenberg M. , Kikutani M.
Published: August 2015

Bovine growth hormone, subjected to DEAE-cellulose chromatography, yielded one major and several minor components. The various chromatographic fractions of bovine growth hormone were compared with the parent material for their ability to promote hormone effects in vivo and in vitro. The major component of bovine growth hormone was homogeneous by acrylamide-gel electrophoresis, rechromatography and sedimentation equilibrium. Its amino acid composition was similar to that of the parent hormone. The major component possessed all the qualitative activities present in the original heterogeneous material, including promotion of acute hypoglycaemia and hypolipaemia. In studies in vitro in adipose-tissue segments the major component of the hormone increased entry of glucose and its oxidation to CO2, conversion of glucose into glyceride glycerol, release of glycerol and incorporation of histidine into adiposetissue protein. Other chromatographic fractions of bovine growth hormone were not homogeneous and possessed some but not all of the metabolic activities attributed to the hormone preparations or its major component. Thus, the metabolic effects obtained with bovine growth-hormone preparations in vivo and in vitro can be obtained with the major homogeneous component of the hormone. This observation precludes the possibility that the metabolic effects obtained with bovine growth-hormone preparations are due to the combined actions of a number of components found therein.
Glycosaminoglycans of cat invertebral disc
Authors: Butler W. F. , Wels C. M.
Published: August 2015

The glycosaminoglycan contents of samples from cat intervertebral discs were examined by using cetylpyridinium chloride salt elution techniques. The values obtained related to the region of the vertebral column from which they were derived, to the area of the disc, and to water content. In wet tissue there was a significant difference between regions of the vertebral column and between areas of the disc and findings agreed with previous histological reports. The greater part of the glycosaminoglycans present consisted of chondroitin sulphate and dermatan sulphate with smaller amounts of hyaluronic acid; little keratan sulphate was found. The maximum amounts of chondroitin sulphate and dermatan sulphate occurred in the 0.5m-magnesium chloride fractions usually, but moved towards higher molar concentrations in samples derived from some sites, particularly in the lumbar region. Mean values for the water content of the areas of the disc were: nucleus pulposus, 82.4%; inner anulus, 65.6%; outer anulus, 50.5%. The water content was directly related to the amounts of chondroitin sulphate and dermatan sulphate.
Dielectric dispersion in aqueous solutions of oxyhaemoglobin and carboxyhaemoglobin
Authors: Grant E. H. , South G. P. , Takashima S. , Ichimura H.
Published: August 2015

The relative permittivity and conductivity of aqueous solutions of oxyhaemoglobin and carboxyhaemoglobin were measured over the frequency range 150kHz–100MHz. To minimize errors of measurement the investigations were carried out with three different samples of each type of haemoglobin, independent apparatus being used in two different laboratories. The dielectric increment and relaxation time were calculated at each of several temperatures from the results. These lead to a dipole moment of 400 Debyes and an activation enthalpy of 17.6±1.4kJ·mol−1, both of which were found to be independent of temperature to within experimental error over the range 3–35°C. The value of the dipole moment shows that the distribution of charge throughout the haemoglobin molecule is nearly symmetrical with respect to the centre of charge. The magnitude of the activation enthalpy is similar to that of the viscosity of water, in accord with the common observation that dielectric relaxation and viscosity are related phenomena. No significant differences are found between the dielectric parameters of oxyhaemoglobin and carboxyhaemoglobin. Combining the results with those obtained from X-ray diffraction of the solid a hydration value of 0.45g of water/g of protein is suggested, subject to the limitations of the model used. Finally, the results indicate the presence of a subsidiary dispersion, which could be attributed to the above quantity of bound water having a static permittivity of about 100 and a relaxation frequency in the region 100–200MHz.
Histone phosphokinase activity in nuclear and cytoplasmic cell fractions from normal and regenerating rat livers
Authors: Siebert G. , Ord Margery G. , Stocken L. A.
Published: August 2015

1. Liver cell fractions were prepared by non-aqueous procedures and nuclei were also obtained in a hyperosmotic sucrose medium. Histone phosphokinase activity, assayed with histone F1 as substrate, was present in the soluble fraction of the cytoplasm and also bound on to the chromatin fraction of the nucleus. 2. The activity of the enzyme increased sixfold in nuclei from regenerating livers 22h after partial hepatectomy. 3. The enzyme bound in the nucleus was only marginally activated by 1μm-3′:5′-cyclic AMP which stimulated the cytoplasmic soluble enzyme fourfold. 4. Nuclei prepared by the non-aqueous technique were also able to phosphorylate histones F2a and F3 and showed histone phosphatase activity with histone F1 phosphate as substrate.
Inhibition of adenosine 5′-triphosphate–creatine phosphotransferase by substrate–anion complexes. Evidence for the transition-state organization of the catalytic site
Authors: Milner-White E. J. , Watts D. C.
Published: August 2015

1. The substrate combination creatine–MgADP does not significantly protect creatine kinase against inhibition by iodoacetamide in the absence of small anions. 2. Small anions can be divided into three groups according to the way in which they affect creatine kinase: I, acetate reversibly increases enzyme activity in the forward reaction but does not affect the rate of inhibition by iodoacetamide in the presence of creatine plus MgADP; II, planar anions and some halides (HCO3−, HCO2−, NO3−, NO2−, Cl−, Br−, F−) in the presence of creatine plus MgADP protect the enzyme from inhibition by iodoacetamide; III, tetrahedral anions (SO42−, HPO42−, ClO4−, BF4−) and iodide do not affect the rate of inhibition by iodoacetamide in the presence of creatine plus MgADP but may decrease the protection by class II anions under these conditions. Anions of class II and class III also reversibly inhibit enzyme activity. 3. It is concluded that class II anions form a stable and inactive quaternary enzyme–creatine–MgADP–anion complex and this is responsible for the effect attributed by previous workers to the ternary complex lacking anion. Formation of this complex, particularly in the forward reaction, can lead to markedly non-linear enzyme progress curves. Some previous observations are re-appraised in the light of these findings. 4. From the behaviour of chloride and nitrate ions, and the marked lowering of the Ki values for creatine and MgADP they produce, it is inferred that planar or monoatomic anions act in the quaternary complex by simulating the transferable phosphoryl group in the transition state (or another intermediate state) of the reaction. 5. It is suggested that, in the course of the reaction, the tetrahedral phosphate-binding site for the transferable phosphoryl group of the substrate (that also binds class II and class III anions) changes into a trigonal bipyramid site (also occupied by class II anions). This strains the phosphoryl group to adopt the transitional sp3d hybridized state and must contribute significantly to the low activation energy of the reaction. 6. Catalysis is deduced to proceed by an ‘in line’ transfer reaction and from the effects of class II anions it is possible to estimate the approximate dimensions of the anionic site in the transition-state complex. 7. The specific protecting effect of an equilibrium mixture of substrates against inhibition by iodoacetamide provides further evidence for the conformational change suggested above as a step in the catalytic process.
Bile salts of germ-free domestic fowl and pigs
Authors: Haslewood G. A. D.
Published: August 2015

1. The bile of germ-free domestic fowl contains taurine conjugates of 3α,7α-dihydroxy-5β-cholan-24-oic acid (chenodeoxycholic acid), 3α,7α,12α-trihydroxy-5β-cholan-24-oic acid (cholic acid) and its 5α-epimer (allocholic acid): that of germ-free pigs contains glycine and taurine conjugates of chenodeoxycholic acid, 3α,6α-dihydroxy-5β-cholan-24-oic acid (hyodeoxycholic acid), 3α,6α,7α-trihydroxy-5β-cholan-24-oic acid (hyocholic acid) and (probably) cholic acid. Keto acids were not found. 2. Allocholic acid and hyodeoxycholic acid are thus proved to be primary bile acids in intact animals. 3. The evolutionary and biochemical implications of these findings are briefly considered.
Androgen dynamics in vitro in the normal and hyperplastic human prostate gland
Authors: Giorgi Eleonora P. , Stewart Joan C. , Grant J. K. , Scott R.
Published: August 2015

The dynamics of uptake and metabolism in vitro of androgens by normal and hyperplastic human prostate glands was studied by means of a new experimental design proposed by Gurpide & Welch (1969). Prostate slices were perfused with a medium containing [3H]testosterone and [14C]androstenedione, or 5α-dihydro-[3H]testosterone and [14C]testosterone. The entry into the slices, the irreversible metabolism, the conversion between the compounds and the tissue retention or ‘uptake’ of the steroids were measured at the steady state. A similar portion of the three androgens entered the tissue and was irreversibly metabolized. Conversion of testosterone into 5α-dihydrotestosterone was much greater than the interconversion of testosterone and androstenedione. The prostate slices retained 5α-dihydrotestosterone at a concentration three times that in the medium, whereas testosterone and androstenedione were retained to a smaller extent. At a steroid concentration of 0.11μmol/l in the medium, the various parameters did not differ significantly in experiments performed with slices from normal and hyperplastic glands. When the steroid concentration in the medium was increased tenfold, however, a difference between normal and hyperplastic glands was evident. The normal glands increased the uptake and metabolism proportionally to the elevation of the steroid concentration in the medium. In the hyperplastic glands the entry and metabolism lagged behind the increase in steroid supply, whereas the tissue uptake became disproportionately high. The possible causes of this finding are discussed.