bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of glycosidases by aldonolactones of corresponding configuration. The specificity of α-l-arabinosidase
Authors: Conchie J. , Gelman A. L. , Levvy G. A.
Published: August 2015

1. The previous study (Conchie, Gelman & Levvy, 1967b) of the specificity of β-glucosidase, β-galactosidase and β-d-fucosidase in barley, limpet, almond emulsin and rat epididymis was extended to α-l-arabinosidase. 2. The inhibitory action of l-arabinono-(1→5)-lactone was tested against all four types of enzyme, and α-l-arabinosidase was examined for inhibition by glucono-, galactono- and d-fucono-lactone. 3. In emulsin, the enzyme that hydrolyses β-glucosides, β-galactosides and β-d-fucosides also hydrolyses α-l-arabinosides. Rat epididymis resembles emulsin except that, as already noted, it lacks β-glucosidase activity. 4. In the limpet, α-l-arabinosidase activity is associated with the enzyme that hydrolyses β-glucosides and β-d-fucosides, and not with the separate β-galactosidase. 5. The effects of the different lactones on the barley preparation suggest that α-l-arabinosidase activity is associated with the β-galactosidase rather than with the enzyme that hydrolyses β-glucosides and β-d-fucosides. Fractionation and heat-inactivation experiments indicate that there is also a separate α-l-arabinosidase in the preparation.
A new enzyme for the interconversion of pyruvate and phosphopyruvate and its role in the C4 dicarboxylic acid pathway of photosynthesis
Authors: Hatch M. D. , Slack C. R.
Published: August 2015

1. An enzyme was isolated from leaves of tropical grasses that catalyses the reversible conversion of pyruvate, ATP and orthophosphate into phosphopyruvate, AMP and pyrophosphate. A requirement for Mg2+ could not be replaced by Mn2+ or Ca2+. 2. By replacing orthophosphate with [32P]orthophosphate or with arsenate, evidence was provided that the orthophosphate consumed appears in pyrophosphate. 3. Without Mg2+ or 2-mercaptoethanol the enzyme was rapidly and irreversibly inactivated. EDTA only partially replaced the requirement for the thiol compound. The enzyme was considerably more unstable at 0° or when frozen than at 22°. Even with the best conditions devised the enzyme lost about 25% of its activity every 3hr. 4. The activities of the enzyme in leaves of the tropical grasses sugar cane (Saccharum hybrid var. Pindar), maize (Zea mays) and sorghum (Sorghum vulgare) were comparable with their maximum photosynthesis rates. The enzyme was not detectable in leaf extracts from several other plants. 5. Its role in photosynthesis is discussed.
The inhibitory effects in vitro of phenothiazines and other drugs on lipid-peroxidation systems in rat liver microsomes, and their relationship to the liver necrosis produced by carbon tetrachloride
Authors: Slater T F
Published: August 2015

1. The effects of several phenothiazine derivatives on lipid-peroxidation systems in rat liver microsomes were studied and the results are considered in relation to the hepatotoxic action of carbon tetrachloride. 2. The lipid-peroxidation system coupled to NADPH2 oxidation and stimulated by an ADP–Fe2+ mixture is strongly inhibited in vitro by promethazine (50% inhibition at 29μm). Chlorpromazine and Stelazine also inhibit the peroxidation system but are less effective than promethazine. 3. The effects of promethazine on three other systems involving oxygen uptake (sulphite oxidation, orcinol oxidation and mitochondrial succinate oxidation) were also studied. Promethazine does not inhibit these systems to the same extent as it does the NADPH2–ADP–Fe2+ lipid-peroxidation system. 4. Promethazine also produces an inhibition of the NADPH2–ADP–Fe2+ system in liver microsomes after administration in vivo. It is concluded that the inhibition involves the interaction of the drug (or a metabolite of it) with the microsomal electron-transport chain. 5. Several other compounds known to protect the rat against liver necrosis after the administration of carbon tetrachloride were tested for inhibitory action on the NADPH2–ADP–Fe2+ system. No clear correlation was observed between effectiveness in vivo as a protective agent and inhibitory effects on the NADPH2–ADP–Fe2+ system in vitro. 6. Promethazine was found to inhibit the stimulation of lipid peroxidation produced in rat liver microsomes by low concentrations of carbon tetrachloride. This effect occurs at a concentration similar to that observed in vivo after administration of a normal clinical dose.
Leucyl-β-naphthylamide-splitting enzymes in the mammalian endocrine pancreas
Authors: Idahl L.-Å. , Täljedal I.-B.
Published: August 2015

The proteolytic capacity of the endocrine pancreas in obese–hyperglycaemic mice was evaluated by using the chromogenic substrate l-leucyl-β-naphthylamide (LNA). The analytical sensitivity obtained with this substrate in photometric and fluorimetric assays permitted quantitative determinations of C–N-bond-splitting activity in both crude islet homogenates and electrophoretic fractions thereof. The following observations were made: (1) The rate of LNA cleavage was maximal at about pH7 in islets as well as in acinar tissue. An apparent Km of 4×10−5–6×10−5m was calculated for both the endocrine and exocrine pancreas. (2) The level of LNA-splitting enzyme activity was of the same magnitude in the islets as in the liver, and significantly higher in the islets than in the exocrine pancreas. Starving the animals for 7 days did not affect the enzyme activity levels. (3) Two distinct LNA-splitting enzymes could be separated from the pancreatic islets by means of disc electrophoresis, the most rapidly migrating band representing the highest activity. Though similar electrophoresis patterns were obtained with acinar tissue and liver, only one enzyme could be demonstrated in serum. The data suggest that the β-cells, in addition to being highly specialized for the production of a specific protein, contain a comparatively high capacity for protein catabolism.
Purification and properties of an amine dehydrogenase from Pseudomonas AM1 and its role in growth on methylamine
Authors: Eady R R , Large P J
Published: August 2015

1. Whole cells of Pseudomonas AM1 grown on methylamine oxidize methylamine, formaldehyde and formate. Crude extracts oxidize methylamine only if supplemented with phenazine methosulphate. 2. By using a spectrophotometric assay, the methylamine-oxidizing enzyme has been purified 20-fold in 31% yield. 3. The enzyme is a dehydrogenase, unable to utilize oxygen, NAD, NADP, flavines or menadione as electron acceptors, but able to utilize phenazine methosulphate, ferricyanide, cytochrome c or brilliant cresyl blue. 4. The enzyme is non-specific, readily oxidizing aliphatic monoamines and diamines, histamine and ethanol-amine. Secondary and tertiary amines, quaternary ammonium salts and aromatic amines are not oxidized. 5. The pH optima for methylamine, n-pentylamine and putrescine are respectively 7·6, 8·0 and 8·5. 6. The Km value for methylamine is 5·2μm and that for phenazine methosulphate 56μm. 7. The enzyme will withstand heating for 15min. at 80° without loss of activity, but is inactivated at higher temperatures. It is not inactivated by any pH value between 2·6 and 10·6. 8. The dehydrogenase is inhibited by semicarbazide (Ki 3·35μm), isoniazid (Ki 1·17μm), cuprizone (Ki 0·49μm), p-chloromercuribenzoate (Ki 0·45mm) and quinacrine (Ki 12·1mm). 9. The enzyme is absent from succinate-grown cells, and, during adaptation from succinate to methylamine, activity appears before growth on methylamine begins.
Biosynthesis of the pyrimidine moiety of thiamine. A new route of pyrimidine biosynthesis involving purine intermediates
Authors: Newell P. C. , Tucker R G
Published: August 2015

1. The pattern of distribution on the purine pathway of mutants of Salmonella typhimurium LT2 that had the double growth requirement for a purine plus the pyrimidine moiety of thiamine (ath mutants) indicated that purines and the pyrimidine moiety of thiamine share the early part of their biosynthetic pathways, and that 4-aminoimidazole ribonucleotide (AIR) is the last common intermediate. Two mutants that at first appeared anomalous were further investigated and found not to affect this deduction. 2. The ribonucleoside form of AIR (AIRs) satisfied the requirements both for a purine and for the pyrimidine moiety of thiamine of an ath mutant. 3. Methionine was required for the conversion of AIR into the pyrimidine moiety. 4. Radioactive AIRs was converted into radioactive pyrimidine moiety by an ath mutant without significant dilution of specific radioactivity. 5. Possible mechanisms for pyrimidine-moiety biosynthesis from AIR are discussed.
The role of the regulator-gene product (repressor) in catabolite repression of β-galactosidase synthesis in Escherichia coli
Authors: Palmer J. , Moses V.
Published: August 2015

1. The specific role of the lac repressor (i-gene product) in transient catabolite repression evoked by the introduction of glucose into the medium has been investigated in Escherichia coli by using mutants of the i-gene. 2. A temperature-sensitive mutant (iTL) is normally inducible and demonstrates transient repression when grown at 32°. At 42° it is about 20% constitutive and transient catabolite repression is abolished. 3. A strain carrying an amber suppressor-sensitive mutation in the i-gene is phenotypically constitutive and also fails to show transient catabolite repression. 4. Insertion of Flaci+ into this strain restores both inducibility and transient repression. 5. It is concluded that the i-gene product interacts with the catabolite co-repressor in such a way that its affinity for the operator is increased.
The kinetics of the reaction of nitrophenyl phosphates with alkaline phosphatase from Escherichia coli
Authors: Trentham D. R. , Gutfreund H.
Published: August 2015

1. The steady-state rate of hydrolysis of 2,4-dinitrophenyl phosphate catalysed by Escherichia coli phosphatase is identical with that of 4-nitrophenyl phosphate over the pH range 5·5–8·5. 2. The increase in the rate of the enzyme-catalysed decomposition of nitrophenyl phosphates in the presence of tris at pH8·1 and 5·9 is consistent with the hypothesis that tris increases the rate of decomposition of a phosphoryl-enzyme intermediate. At pH8·1 the rate of decomposition of the phosphoryl-enzyme is approximately twice as fast as the rate of its formation, whereas at pH5·9 the rate of formation of the phosphoryl-enzyme is considerably faster than its decomposition. 3. Pre-steady-state measurements of the initial transient of the liberation of 2,4-dinitrophenol during the reaction of the enzyme with 2,4-dinitrophenyl phosphate confirmed the above pH-dependence of the ratio of the rates of phosphorylation and dephosphorylation of the enzyme. At optimum pH (above pH8), when the phosphorylation of the enzyme by the substrate is rate-determining, this step must be controlled by a rearrangement of the enzyme or enzyme–substrate complex.
Investigations on vitamin D esters synthesized in rats. Detection and identification
Authors: Fraser D. R. , Kodicek E.
Published: August 2015

1. Vitamin D-deficient rachitic rats were given [1−3H]cholecalciferol by gastric intubation. After 24hr., diethyl ether extracts of liver and kidney contained 5–11% and 4·5–20% respectively of total vitamin D apparently esterified with long-chain fatty acids. 2. A two-dimensional thin-layer chromatographic technique was devised that completely separated seven synthetic vitamin D esters according to the chain length and number of double bonds in the fatty acid component. When the ‘vitamin D ester’ fraction from liver or kidney was co-chromatographed with the standard esters, radioactivity appeared mainly in vitamin D palmitate, stearate, oleate and linoleate regions. The proportion of radioactivity in the saturated fatty acid esters was higher in kidney than in liver. 3. The same percentage of tissue vitamin D in the esterified form was found at each of two dosages of vitamin D. 4. The possible specificity of a vitamin D esterification mechanism is discussed.
Investigations on vitamin D esters synthesized in rats. Turnover and sites of synthesis
Authors: Fraser D. R. , Kodicek E.
Published: August 2015

1. The tissue contents of vitamin D alcohol and ester were estimated in rats 5, 10, 24, 48 and 72hr. after peroral administration of [1−3H]cholecalciferol. 2. The total vitamin D in liver decreased in an exponential fashion from 19% of the dose at 5hr. to 0·6% at 72hr., but the ester content remained at a relatively constant low value from 5hr., so that by 72hr. it represented 67% of the total vitamin D. Vitamin D ester in kidney increased slowly to 48hr., but by 72hr. it was only 10% of the total vitamin D. 3. The small intestine, unlike liver and kidney, contained a higher content of vitamin D ester 10hr. after administration than at later times, and it is postulated that some vitamin D was esterified during absorption from the alimentary tract. 4. Plasma contained vitamin D ester at all time intervals, and it is suggested that ester found in liver and kidney could have been transported to these sites in the blood. 5. Thoracic-duct lymph was found to transport 43% of a peroral dose of vitamin D in 12hr., of which 1·4% was esterified. The fatty acid components of the lymph vitamin D ester, determined by two-dimensional thinlayer chromatography, were mainly palmitate (31%), stearate (25%), oleate (16%) and linoleate (16%). This pattern was similar to that previously found in liver.
The isolation of neurophysin-I and -II from bovine pituitary neurosecretory granules separated on a large scale from other subcellular organelles. Demonstration of slow equilibration of neurosecretory granules during centrifugation in a sucrose density gradient
Authors: Dean C. R. , Hope D B
Published: August 2015

1. An improved procedure for the isolation of neurosecretory granules from the posterior lobe of the bovine pituitary gland is described. 2. Of the total oxytocic and pressor activities present in the original tissue 80% was sedimentable. 3. The granules were separated from mitochondria by prolonged centrifugation in a sucrose density gradient. During a sedimentation period of 5hr. the granules moved progressively into denser regions of the gradient and the mitochondria remained at the top. 4. The biological activities of the granules were measured: the oxytocic activity was 11·56±1·63 and the pressor activity was 15·60±3·91 units/mg. of protein. 5. A protein was isolated from a lysate of granules prepared from 40 pituitary glands. Amino acid analysis showed that it consisted of a mixture of neurophysin-I and neurophysin-II in equal proportions. It accounted for 60% of the soluble granule protein and for 50% of the total granule protein. 6. The neurophysins present in the granules are associated with 19·1 units of oxytocic and 21·1 units of pressor activity/mg. of protein. 7. Starch-gel electrophoresis revealed the presence of both neurophysins in extracts of 15 pituitary glands studied individually. 8. We conclude that the polypeptide hormones, oxytocin and [8-arginine]-vasopressin, are normally closely associated with the two neurophysins within neurosecretory granules of the pituitary gland.
The effect of molybdenum on ascorbic acid metabolism in rats
Authors: Sasmal N. , Kar N. C. , Mukherjee Dipti , Chatterjee G. C.
Published: August 2015

1. The effect of dietary molybdenum on the growth rate and also on ascorbic acid metabolism in rats was studied. An excess of dietary molybdenum resulted in growth retardation and loss of weight. Tolerance to molybdenum was affected by the nature of the molybdenum salt administered. 2. Molybdenum ingestion altered certain aspects of ascorbic acid metabolism in rats. The conversion of d-glucuronolactone into l-ascorbic acid in vitro and the oxidative breakdown of l-ascorbic acid by liver enzymes decreased with high molybdenum intakes. The activity of liver uronolactonase was slightly inhibited. The activities of l-gulonate dehydrogenase and l-gulonate decarboxylase were not affected appreciably. 3. Molybdenum supplementation of the control diet resulted in an increase in ascorbic acid content of spleen and adrenal gland, and in a marked decrease in the urinary excretion of ascorbic acid and glucuronic acid. The implications of these findings are discussed.
The ‘neurotoxicity’ of l-2,4-diaminobutyric acid
Authors: O'Neal Robert M. , Chen Chung-Ho , Reynolds Carol S. , Meghal Sharadchandra K. , Koeppe Roger E.
Published: August 2015

The neurolathyrogen l-2,4-diaminobutyric acid is concentrated by liver, and liver damage can yield neurotoxicity; thus the neurotoxicity caused by this compound may be due to liver damage followed by secondary brain damage. 1. The intraperitoneal administration of toxic doses of l-2,4-diaminobutyric acid to rats resulted in hyperirritability, tremors and convulsions in 12–20hr. and increased the concentration of ammonia of blood and brain slightly and the concentration of glutamine of brain two- to three-fold. By contrast, toxic doses of l-homoarginine, l-lysine, l-leucine and ammonium acetate caused dyspnoea, extreme prostration, and in some cases coma in 15–30min., and increased the concentration of ammonia of blood significantly and the concentration of glutamine of brain slightly. These results indicate that l-2,4-diaminobutyric acid caused a chronic ammonia toxicity, whereas the other amino acids and ammonium acetate resulted in an acute ammonia toxicity. 2. Liver slices from l-2,4-diaminobutyric acid-treated animals and normal liver slices preincubated with l-2,4-diaminobutyric acid utilized ammonia and formed urea at a lower rate than control slices from normal rats. 3. l-2,4-Diaminobutyric acid inhibited competitively ornithine carbamoyltransferase of rat liver homogenates, thus demonstrating that this reaction is a primary site of toxicity for this neurolathyrogen. Although we were unable to show marked elevations of blood ammonia concentration after treatment with l-2,4-diaminobutyric acid, these results are interpreted to mean that ammonia utilization (urea synthesis) in liver is inhibited by l-2,4-diaminobutyric acid and that at least part of the neurotoxicity is due to a prolonged slight increase in body ammonia concentration.
Incorporation of dl-[2−14C]ornithine and dl-[5−14C]arginine in milk constituents by the isolated lactating sheep udder
Authors: Verbeke R. , Peeters G. , Massart-Leën Anne Marie , Cocquyt G.
Published: August 2015

1. Lactating mammary glands of sheep were perfused for several hours in the presence of dl-[2−14C]ornithine or dl-[5−14C]arginine and received adequate quantities of acetate, glucose and amino acids. 2. In the [14C]ornithine experiment 1·4% of the casein and 1% of the expired carbon dioxide came from added ornithine; 96% of the total radioactivity in casein was recovered in proline; 13% of the proline of casein originated from plasma ornithine. 3. In this experiment the results of chemical degradation of proline of casein as well as relative specific activities in the isolated products are consistent with the view that ornithine is metabolized, by way of glutamic γ-semialdehyde, to proline or glutamic acid. 4. In the [14C]arginine experiments 3% of the casein and 1% of the expired carbon dioxide came from arginine; 84% of the arginine and 9% of the proline of casein originated from plasma arginine. 5. In these experiments the relative specific activities of arginine, ornithine and proline in plasma are in agreement with the view that arginine is metabolized by way of ornithine to proline. The conversion of arginine into ornithine is probably catalysed by arginase, so that arginase in mammary tissue may be involved in the process of milk synthesis.
The interaction of triethyltin with components of animal tissues
Authors: Rose M. S. , Aldridge W. N.
Published: August 2015

1. The distribution of triethyl[113Sn]tin chloride in the rat, guinea pig and hamster is not uniform, the highest concentrations being in rat blood and the liver of all three species. 2. Subcellular fractionation of rat liver, brain and kidney shows that triethyltin binds to all fractions to different extents. In the liver of the rat and guinea pig the supernatant fraction contains the largest amount and the highest specific concentration; this triethyltin is bound to a non-diffusible component. 3. Rat haemoglobin is responsible for the binding of triethyltin in rat blood (2 moles of triethyltin/mole of haemoglobin). Haemoglobins from other species have much less affinity for triethyltin. 4. A variety of other proteins do not bind triethyltin.
The kinetics of a novel cyclic reaction system and its use in the assay of polynucleotide phosphorylase or adenosine diphosphate plus adenosine triphosphate
Authors: Wilson R. J. H. , Lilly M. D.
Published: August 2015

1. A sensitive new method is described for the rapid optical assay of polynucleotide phosphorylase in crude bacterial extracts of low specific activity. 2. The assay is non-linear with time and a quick method for determining the approximate activity by using a nomograph is given. 3. The dependence of the assay on Mg2+ concentration was investigated and the conditions that gave first-order kinetics were determined. 4. The theoretical behaviour of the system was examined mathematically and shown to tend to a simple dynamic steady state, under certain conditions. 5. The potential uses of such cyclic systems are discussed.
The pathway of biosynthesis of nicotinamide–adenine dinucleotide in rat mammary gland
Authors: Greenbaum A. L. , Pinder S.
Published: August 2015

1. The pathway of NAD synthesis in mammary gland was examined by measuring the activities of some of the key enzymes in each of the tryptophan, nicotinic acid and nicotinamide pathways. 2. In the tryptophan pathway, 3-hydroxyanthranilate oxidase and quinolinate transphosphoribosylase activities were investigated. Neither of these enzymes was found in mammary gland. 3. In the nicotinic acid pathway, nicotinate mononucleotide pyrophosphorylase, NAD synthetase, nicotinamide deamidase and NMN deamidase were investigated. Both NAD synthetase and nicotinate mononucleotide pyrophosphorylase were present but were very inactive. Nicotinamide deamidase, if present, had a very low activity and NMN deamidase was absent. 4. In the nicotinamide pathway both enzymes, NMN pyrophosphorylase and NMN adenylyltransferase, were present and showed very high activity. The activity of the pyrophosphorylase in mammary gland is by far the highest yet found in any tissue. 5. The apparent Km values for the substrates of these enzymes in mammary gland were determined. 6. On the basis of these investigations it is proposed that the main, and probably only, pathway of synthesis of NAD in mammary tissue is from nicotinamide via NMN.
A blocked N-terminal residue in the light chain of rabbit immunoglobulin G
Authors: Rüde E. , Givol D.
Published: August 2015

The light chain of rabbit immunoglobulin G was shown to contain 15–20% blocked N-terminal residue. The blocked residue is pyrrolid-2-one-5-carboxylic acid, and most of the chains that contain this residue have the N-terminal sequence pyrrolid-2-one-5-carbonyl-valine.
Enzymes of the mandelate pathway in bacterium N.C.I.B. 8250
Authors: Kennedy S. I. T. , Fewson C A
Published: August 2015

1. Bacterium N.C.I.B. 8250 was grown on dl-mandelate, benzyl alcohol, benzoyl-formate, benzaldehyde and benzoate and also on 2-hydroxy, 4-hydroxy, 3,4-dihydroxy and 4-hydroxy-3-methoxy analogues of these compounds. The enzymic complements of the cells were determined and the specificities of some of the enzymes examined. 2. Growth on mandelate or benzoylformate induces l-mandelate dehydrogenase, benzoylformate decarboxylase, benzyl alcohol dehydrogenase and a heat-stable as well as a heat-labile benzaldehyde dehydrogenase. Growth on benzyl alcohol or benzaldehyde induces benzyl alcohol dehydrogenase and the heat-labile benzaldehyde dehydrogenase. 3. The enzymes of the mandelate-to-benzoate pathway are non-specifically active on, and induced by, all the substituted analogues that support growth. 4. Benzoate oxidase is induced by growth on benzoate or on 2-hydroxybenzoate. 2-Hydroxybenzoate hydroxylase, 4-hydroxybenzoate hydroxylase and 4-hydroxy-3-methoxybenzoate O-demethylase are induced only by growth on homologous substrates. 5. The results of the investigation are discussed with regard to the possible regulation of the enzyme systems.
The regulation of protein synthesis in the liver of rats. Mechanisms of dietary amino acid control in the immature animal
Authors: Wannemacher R. W. , Cooper W. K. , Yatvin M. B.
Published: August 2015

Weanling (23-day-old) rats were fed either on an amino acid-deficient diet (6% of casein, which in effect represents an ‘amino acid-deficient’ diet) or on a diet containing an adequate amount of protein (18% of casein) for 28 days. The hepatic cells from the animals fed on the low-protein diet were characterized by low amino acid content, almost complete inhibition of cell proliferation and a marked decrease in cell volume, protein content and concentration of cytoplasmic RNA compared with cells from control rats. The lower concentration of cytoplasmic RNA was correlated with a decreased ribosomal-RNA content, of which a larger proportion was in the form of free ribosomes. The protein-synthetic competence and messenger-RNA content of isolated ribosomes from liver cells of protein-deprived animals were 40–50% of those noted in controls. At 1hr. after an injection of radioactive uridine, the specific radioactivity of liver total RNA was greater in the group fed on the low-protein diet, but the amount of label that was associated with cytoplasmic RNA or ribosomes was significantly less than that noted in control animals. From these data it was concluded that dietary amino acids regulate hepatic protein synthesis (1) by affecting the ability of polyribosomes to synthesize protein and (2) by influencing the concentration of cytoplasmic ribosomes. It is also tentatively hypothesized that the former process may be directly related to the concentration of cellular free amino acids, whereas the latter could be correlated with the ability of newly synthesized ribosomal sub-units to leave the nucleus.
Properties of β-lactamases produced by three species of mycobacteria
Authors: Kasik J. E. , Peacham Lin
Published: August 2015

1. Mycobacterium smegmatis (N.C.T.C. 8158), M. fortuitum and M. phlei (MPI) produce a constitutive β-lactamase that has penicillinase and cephalosporinase activity. 2. The β-lactamases of these three species of acid-fast bacteria were mainly cell-bound, only small amounts of activity being liberated into the extracellular fluid. The total β-lactamase activity of these mycobacteria was much lower than that of certain Gram-positive organisms, but comparable with that reported for species of Gram-negative bacteria. 3. The β-lactamases of intact cells of the mycobacteria were not freely accessible to any of the substrates tested, but the apparent crypticity factor to benzylpenicillin was greater than that to cephaloridine and cephalosporin C. 4. Attempts to induce β-lactamase activity in M. smegmatis and M. phlei failed even with high concentrations of inducer. 5. The β-lactamases obtained from the three species of mycobacteria showed different substrate specificities, including different relative activities as cephalosporinases and penicillinases respectively. 6. Certain derivatives of 6-aminopenicillanic acid and 7-aminocephalosporanic acid were found to be resistant to hydrolysis by β-lactamases of M. smegmatis and M. fortuitum. 7. The β-lactamase of M. smegmatis was competitively inhibited by a number of β-lactamase-resistant derivatives of 6-aminopenicillanic acid, but not by similar derivatives of 7-aminocephalosporanic acid.
The effects of copper and other ions on the ribonucleic acid polymerase activity of isolated rat liver nuclei
Authors: Novello F. , Stirpe F.
Published: August 2015

1. The effects of various ions on the Mg2+- and Mn2+/ammonium sulphate-activated RNA polymerase activities of isolated liver nuclei were studied. 2. The Mg2+-activated RNA polymerase reaction was inhibited by more than 60% by Cd2+, SeO32−, Be2+, Cu2+, Co2+, Ca2+ and La3+, all at 1mm concentrations. 3. The Mn2+/ammonium sulphate-activated RNA polymerase reaction was strongly inhibited by Hg2+, Cd2+, Cu2+ and Ag+. The effect of Hg2+, Cd2+ and Ag+ was relieved by cysteine or mercaptoethanol. 4. Inhibition by Cu2+ was not affected by addition of DNA, and was relieved only partially by EDTA or histidine. 5. No changes of RNA polymerase activities were observed in nuclei isolated from the liver of rats treated with copper albuminate.
Biosynthesis of ethylene. Methanesulphinic acid as cofactor in the enzymic formation of ethylene from methional
Authors: Mapson L. W. , Self R. , Wardale D. A.
Published: August 2015

The second cofactor in the peroxidase-catalysed formation of ethylene from methional in cauliflower extracts was identified as methanesulphinic acid. The progress of the reaction is described and the activities of related sulphinic acids were determined.
A phosphorylation site in brain and the delayed neurotoxic effect of some organophosphorus compounds
Authors: Johnson M K
Published: August 2015

1. It is proposed that part of a neurotoxic dose of di-isopropyl phosphorofluoridate will be covalently bound in vivo to a specific component in the brain and spinal cord as the initial biochemical event in the genesis of the lesion. 2. A test system in vitro was devised that removes many di-isopropyl phosphorofluoridate-binding sites and indicates that the specific component may be a protein present in brain at a concentration comparable with that of the cholinesterases. 3. The site was found to be present and capable of binding di-isopropyl phosphorofluoridate in vitro in brain samples taken from either normal hens or those dosed with organophosphorus esterase inhibitors that are not neurotoxic. 4. Very little of the specific binding activity was found in brain samples from hens pre-dosed with a variety of neurotoxic organophosphorus compounds. 5. A solubilized preparation of the active brain component was obtained, suitable for further purification and study.
Stability of deoxyribonucleic acid methylated in the intact animal by administration of dimethylnitrosamine. Rate of breakdown in vivo and in vitro at different dosages
Authors: Craddock Valda M.
Published: August 2015

1. The effect of administration of various dosages of dimethylnitrosamine on the extent of methylation of liver and kidney nucleic acids in the intact rat was studied. Methylation of liver nucleic acids was linearly related to the dosage, but decreasing the dose produced relatively less lowering of the extent of alkylation of kidney nucleic acids. 2. The rates of disappearance of 7-methylguanine from DNA during the 2 days after administration of dimethylnitrosamine in the intact animal and on incubation under simulated physiological conditions in vitro were compared. At a high dosage this rate was greater in vivo than in vitro. At a low dosage the small difference between the two rates was not thought to be sufficient evidence for existence of a specific enzymic excision of the abnormal base.
The action of certain antibiotics on mitochondrial, erythrocyte and artificial phospholipid membranes. The role of induced proton permeability
Authors: Henderson P. J. F. , McGivan J. D. , Chappell J. B.
Published: August 2015

1. The action of the antibiotics enniatin A, valinomycin, the actin homologues, gramicidin, nigericin and dianemycin on mitochondria, erythrocytes and smectic mesophases of lecithin–dicetyl hydrogen phosphate was studied. 2. These antibiotics induced permeability to alkali-metal cations on all three membrane systems. 3. The ion specificity on each membrane system was the same. 4. Enniatin A, valinomycin and the actins did not induce permeability to protons, whereas nigericin and dianemycin rendered all three membrane systems freely permeable to protons. 5. Several differences were noted between permeability induced by nigericin and that induced by gramicidin. 6. The action of all these antibiotics on mitochondrial respiration could be accounted for by changes in passive ion permeability of the mitochondrial membrane similar to those induced in erythrocytes and phospholipid membranes, if it is assumed that a membrane potential is present in respiring mitochondria.
β-d-Glucosidases and related enzymic activities in pig kidney
Authors: Abrahams Hope E. , Robinson D.
Published: August 2015

1. The β-glucosidase activity of pig kidney is located in the unsedimentable fraction of the cell and is not associated with the lysosomes. 2. The enzyme is active towards β-d-glucosides, β-d-galactosides, β-d-xylosides and α-l-arabinosides. 3. These activities could not be separated by gel electrophoresis, gel filtration or DEAE-cellulose chromatography. 4. Response to inhibitors, heat-denaturation and competitive substrates suggests that a single active site is responsible for all four activities. 5. Two forms of the enzyme were found to occur either separately or together in kidneys of pigs from several different breeds. 6. Electro-focusing experiments show these to have a small difference in isoelectric point (4·9 and 5·1), and gel filtration gives an approximate molecular weight of 50000 for both forms. 7. The characteristics of these two enzymes are compared.
The reaction of mitochondrial l-3-glycerophosphate dehydrogenase with various electron acceptors
Authors: Dawson A P , Thorne C. J. R.
Published: August 2015

1. The kinetics of the reaction of glycerophosphate dehydrogenase with a variety of electron acceptors have been investigated. 2. In all cases the reaction mechanism appears to involve a free modified-enzyme intermediate. 3. With some electron acceptors, the maximum velocity of the reaction and the Km for glycerophosphate are independent of the nature of the electron acceptor, whereas in other cases this is not so. 4. The reaction mechanism of the enzyme extracted with phospholipase A instead of with Triton X-100 is of a similar type.
Properties and mechanism of action of pyruvate, phosphate dikinase from leaves
Authors: Andrews T. J. , Hatch M. D.
Published: August 2015

1. Sugar-cane leaf pyruvate,Pi dikinase was prepared free of enzymes that would interfere with studies on the stoicheiometry and mechanism of the reaction it catalyses. The reaction was unequivocally shown to involve the conversion of equimolar amounts of pyruvate, ATP and Pi into phosphoenolpyruvate, AMP and PPi. 2. The purified enzyme was stable at pH8·3 only if stored at about 20° in the presence of Mg2+ and a thiol-reducing reagent, care being taken to prevent the oxidation of the thiol. 3. The apparent Michaelis constants for phosphoenolpyruvate and PPi were 0·11mm and 0·04mm respectively and that for AMP was less than 4μm. 4. At pH8·3 the initial velocity of the reaction was about 6 times as fast in the direction towards phosphoenolpyruvate synthesis as in the reverse direction. 5. With the exception of ATP, all the products of the reaction in both directions were inhibitory. 6. The phosphate groups of PPi were derived from Pi and from the terminal phosphate of ATP. 7. Isotope-exchange studies indicated that the reaction proceeds in the following steps:

Enzyme+ATP+Pi ⇌ Enzyme–P+AMP+PPi

Enzyme–P+pyruvate ⇌ Enzyme+phosphoenolpyruvate
Relationship between intracellular amino acids and protein synthesis in the extensor digitorum longus muscle of rats
Authors: Hider R. C. , Fern E. B. , London D. R.
Published: August 2015

1. The incorporation into protein, and the accumulation into the free amino acid pools, of radioactive l-leucine and glycine was studied in rat extensor digitorum longus muscle. 2. The tissue was incubated first with 14C-labelled and then with 3H-labelled amino acid. 3. The experimental results were consistent with a model based on the premise that the amino acids in protein were incorporated directly from the extracellular pool.
A comparative study of the effect of aflatoxin B1 and actinomycin D on HeLa cells
Authors: Harley E. H. , Rees K. R. , Cohen A.
Published: August 2015

1. The cytotoxic effects of aflatoxin B1 on HeLa cells were examined and effects of short exposures of the cells to the toxin were found to be reversible. 2. Aflatoxin B1 inhibited the synthesis of both ribosomal and heterodisperse RNA. It is proposed that the toxin's mechanism of action on ribosomal RNA synthesis is related to its inhibitory effect on the maturation of the 45s-ribosomal-RNA precursor. 3. Protein synthesis is inhibited to a greater extent by aflatoxin B1 than by actinomycin D. In contrast with actinomycin D, aflatoxin B1 was shown to disaggregate polyribosomes directly.
The development of arylsulphatase in the small intestine of the rat
Authors: Danovitch S. H. , Laster L.
Published: August 2015

1. Arylsulphatase activity was measured in stomach, proximal and distal third of small intestine, colon, liver and kidney of foetal and neonatal Sprague–Dawley rats and Swiss mice, with nitrocatechol sulphate as substrate. 2. The specific activity in the distal small intestine, but not in the stomach, proximal small intestine or colon, increased about fourfold between 5 and 16 days after birth in both conventional and germ-free rats. 3. No comparable increase occurred in the distal small intestine of the mouse. 4. The specific activity of acid phosphatase in the distal small intestine of the rat rose only slightly when the arylsulphatase activity increased. 5. The pH optimum and Michaelis constant of arylsulphatase activity of the distal small intestine were similar for 1-day-old, 9-day-old and adult rats. 6. When extracts of distal small intestine of 1-day-old and 9-day-old rats were incubated together, the arylsulphatase activities were additive.
The biosynthesis of rubber from β-hydroxy-β-methylglutaryl-coenzyme A in Hevea brasiliensis latex
Authors: Hepper C. M. , Audley B. G.
Published: August 2015

1. β-Hydroxy-β-methyl[3−14C]glutaryl-CoA is efficiently incorporated into rubber on incubation with Hevea brasiliensis latex, and the incorporation is diminished in the presence of unlabelled mevalonate. β-Hydroxy-β-methylglutaric acid is not utilized for rubber synthesis, but inhibits the formation of rubber from β-hydroxy-β-methylglutaryl-CoA. 2. The incorporation of β-hydroxy-β-methylglutaryl-CoA into rubber is stimulated equally by NADP+ and NADPH and less so by NAD+ and NADH. ATP is slightly stimulatory and CoA is inhibitory. 3. β-Hydroxy-β-methylglutaryl-CoA reductase is concentrated in the sediment (bottom fraction) formed by centrifuging latex at low speed and the enzyme is unstable in the absence of cysteine or GSH. The formation of NADPH takes place in the latex serum. 4. There is a marked seasonal variation in the extent of β-hydroxy-β-methylglutaryl-CoA incorporation into rubber in latex, but mevalonate incorporation is relatively constant. This observation, together with the finding that β-hydroxy-β-methylglutaryl-CoA reduction is the rate-limiting step in the formation of rubber from β-hydroxy-β-methylglutaryl-CoA, suggests that the conversion of β-hydroxy-β-methylglutaryl-CoA into mevalonate is of importance in the regulation of rubber synthesis. 5. Evidence suggesting that β-hydroxy-β-methylglutaryl-CoA lyase is present in H. brasiliensis latex has been obtained.
Compartmentation of terpenoid biosynthesis in green plants. A proposed route of acetyl-coenzyme A synthesis in maize chloroplasts
Authors: Shah S. P. J. , Rogers L J
Published: August 2015

On the basis of radioisotope-incorporation experiments it is suggested that acetyl-CoA, an obligatory intermediate in chloroplast terpenoid biosynthesis, may be formed in maize from photosynthetically fixed carbon dioxide by the route carbon dioxide→glycollate→glyoxylate→glycine→serine→pyruvate→acetyl-CoA. The proposed route is supported by conventional radioisotope-dilution studies and by experiments with inhibitors affecting reactions involved in the pathway. The proposed route appears to play little part in formation of extrachloroplastidic sterol.
Characteristics of β-galactosidase in the mucosa of the small intestine of infant rats. Physicochemical properties
Authors: Kraml Jiří , Koldovský Otakar , Heringová Aleša , Jirsová Věra , Kácl Karel , Ledvina Miloš , Pelichová Hana
Published: August 2015

1. The characteristics of acid and neutral β-galactosidases isolated chromatographically from homogenates of the mucosa of the jejunum and ileum of suckling rats were studied. 2. The minimal molecular weight of the acid β-galactosidase, as estimated by gel filtration on Sephadex G-200, was in the range 83000–105000, whereas for the neutral β-galactosidase the estimated molecular weight was in the range 360000–510000. 3. The acid and neutral β-galactosidases were inhibited competitively by galactono-(1→4)-lactone, with respective Ki values of 0·15mm and 1·1mm. Only the acid β-galactosidase was inhibited competitively by sodium galactonate (Ki 0·17mm). 4. Heat inactivation of both β-galactosidases occurred according to first-order kinetics. The neutral enzyme was more labile, but bovine serum albumin protected acid enzyme only. 5. Urea treatment inactivated both β-galactosidases, the neutral β-galactosidase being more sensitive than the acid β-galactosidase. 6. No differences were found between preparations from the jejunum and ileum.
The delayed neurotoxic effect of some organophosphorus compounds. Identification of the phosphorylation site as an esterase
Authors: Johnson M K
Published: August 2015

1. Organophosphorus compounds that produce a delayed neurotoxic effect in hens phosphorylate a specific site in the brain soon after administration. 2. Phosphorylation of the specific site by di-isopropyl [32P]phosphorofluoridate in vitro is blocked by the prior addition of phenyl phenylacetate. 3. A small proportion of the total activity of hen brain hydrolysing phenyl phenylacetate in vitro was shown to be due to an enzyme different from two others previously described. 4. This enzyme is only slightly inhibited in vitro by concentrations of tetraethyl pyrophosphate and paraoxon (diethyl 4-nitrophenyl phosphate) up to 64μm and is completely inhibited by 6μm-di-isopropyl phosphorofluoridate and 128μm-mipafox. 5. It is also inhibited in vivo by effective doses of neurotoxic organophosphorus compounds but not by high doses of non-neurotoxic analogues. 6. It is deduced that the active site of this enzyme is the phosphorylation site associated with the genesis of delayed neurotoxicity.
Assay, purification and properties of mammalian d-2-hydroxy acid dehydrogenase
Authors: Cammack R.
Published: August 2015

1. A new method is described for the measurement of d-2-hydroxy acid dehydrogenase in samples of animal tissues. 2. The distribution of the enzyme in a number of animals was determined. Of the animal tissues tested, the most active source of the enzyme was found to be rabbit kidney cortex. 3. The enzyme was purified from rabbit kidney to a stage at which it appears to be homogeneous in the analytical ultracentrifuge and on polyacrylamide-gel electrophoresis. 4. The molecular weight was estimated by gel filtration to be approx. 102000; combination of gelfiltration data and the sedimentation coefficient gave a value of 95000. 5. The purified enzyme has a spectrum typical of a flavoprotein. The change induced in the spectrum on addition of d-malate or d-lactate suggests the formation of a flavin semiquinone. 6. Flavin can be removed by treatment with acid ammonium sulphate, and activity can be restored to the inactive apoenzyme by addition of FAD, but not of FMN or riboflavin. 7. Studies of acceptor specificity showed that the enzyme has a relatively weak d-2-hydroxy acid oxidase activity.
Inhibition of bacterial growth by metal salts. The accumulation of ribonucleic acid during inhibition of Escherichia coli by cobalt chloride
Authors: Blundell M. R. , Wild D. G.
Published: August 2015

During inhibition of the growth of Escherichia coli by cobalt chloride protein synthesis was decreased more than the synthesis of RNA. Three species of particle accumulated during the incubation. These had sedimentation coefficients of about 44s, 33s and 23s in tris buffer containing 10 mm-magnesium acetate and 100 mm-potassium chloride, but their sedimentation properties were susceptible to changes in buffer composition. The particles contained RNA but were more readily degraded by ribonuclease than were the ribosomes. RNA isolated from the particles differed slightly in sedimentation properties from the major species of ribosomal RNA. The particles are likely to be closely related to ribosome precursors that have been detected in other circumstances. Changes in the polyribosome fraction during inhibition by cobalt chloride, nickel chloride and chloramphenicol provided further evidence that inhibition by Co2+ involves specific effects on the protein-synthesizing machinery.
Solution structures of ferrihaem in some dipolar aprotic solvents and their binary aqueous mixtures
Authors: Brown S. B. , Lantzke I. R.
Published: August 2015

1. Conductivity and u.v. and visible spectroscopic techniques were used to investigate the solution structure of the prosthetic group of the ferric haemoproteins (ferrihaem) in dimethyl sulphoxide, NN-dimethylacetamide, NN-dimethylformamide and sulpholane, and certain of their aqueous mixtures. 2. In neutral or acid dimethyl sulphoxide, chlorohaemin is monomeric and completely dissociated into Cl−ion and a ferrihaem species with dimethyl sulphoxide molecules in the fifth and sixth co-ordination positions on iron. 3. In neutral NN-dimethylacetamide and NN-dimethylformamide chlorohaemin is monomeric but is largely undissociated, giving different spectra from that of chlorohaemin in dimethyl sulphoxide. On acidification, dissociation occurs and the dimethyl sulphoxide type of spectrum results. 4. Studies in a fourth solvent, sulpholane, indicate that solvent co-ordinating power (ligand strength) rather than bulk dielectric constant is responsible for dissociation of chlorohaemin. 5. In neutral dimethyl sulphoxide–water mixtures chlorohaemin remains monomeric and completely dissociated, and spectra are independent of mixture composition, except at high water concentrations, when precipitation occurs. In alkaline dimethyl sulphoxide–water mixtures, where the complete solvent mixture range is accessible, ferrihaem is polymeric (probably dimeric) and spectra are dependent on solvent composition. A quantitative analysis indicates that the spectral changes are due to replacement by water of one molecule of co-ordinated dimethyl sulphoxide per ferrihaem aggregate, and do not involve a two-molecule replacement as has been suggested for the alkaline pyridine–water system.