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Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hydroxamic acids have been reported to be potent and specific inhibitors of urease (EC 3.5.1.5) activity of plant and bacterial origin. The present investigation was performed on the inhibitory effect of hydroxamic acid derivatives of naturally occurring amino acids on the urease activity of the Jack Bean and the alimentary tracts of rats. Methionine-hydroxamic acid was the most powerful inhibitor (I50=3.9 X 10(-6) M) among nineteen alpha-aminoacyl hydroxamic acids. Phenylalanine-, serine-, alanine-, glycine-, histidine-, threonine-, leucine-, and arginine-hydroxamic acids followed, in order of decreasing inhibitory power. The inhibition proceeded with time at a comparable rate to fatty acyl hydroxamic acid inhibition. The I50 values of alpha-aminoacyl hydroxamic acids were found to be almost equal to those of the corresponding fatty acyl hydroxamic acids. This fact shows that the alpha-amino group did not affect inhibitory power. However, aspartic-beta-, lysine-, and glutamic-gamma-hydroxamic acids, in descending order, were much less inhibitory, probably due to the presence of a carboxyl or omega-amino group. Furthermore, the pH optimum of the inhibition shifted to lower pH in the presence of a carboxyl group, and to a higher pH in e presence of an amino group. The results suggest that the dissociation of an acidic or a basic group reduces the inhibitory power of hydroxamic acid. Hydroxamic acid inhibits urease activity with strict specificity, excpet for aspartic-beta-hydroxamic acid, which inhibited asparaginase competitively. Hydroxamic acid derivatives of amino acids inhibited not only the urease activity of the Jack Bean, but also that of the caecum and ileum parts of the rat intestine.
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PMID:Inhibition of urease activity by hydroxamic acid derivatives of amino acids. 23 68

The naturally occurring modified nucleoside, N-[(9-beta-D-ribofuranosylpurin-6-yl)-N-methylcarbamoyl]-L-threonine (mt6A), and the corresponding glycine analog mg6A were synthesized from N6-methyl-2',3',5'-tri-O-acetyladenosine and the appropriately blocked isocyanates derived from threonine and glycine. The natural mt6A isolated from Escherichia coli tRNA (F. Kimura-Harada et al. (1972), Biochemistry 11, 3910), from wheat embryo tRNA (R. Cunningham and M. W. Gray (1974), Biochemistry 13, 543), and from rat liver tRNA (Rogg et al. (1975), Eur. J. Biochem. 53, 115) was found to be identical with the synthetic mt6A in paper and thin-layer chromatography and electrophoresis. Several analogs of the parent 6-ureidopurine ribonucleoside, N-[(9-beta-D-ribofuranosylpurin-6-yl)carbamoyl]-L-thronine (t6A), were also prepared. Starting from 2',3',5'-tri-O-acetylguanosine and 2',3',5'-tri-O-acetylcytidine and the above isocyanates, the t6A analogs, N-[(9-beta-D-ribofuranosyl-6-oxo-1H-purin-2-yl)carbamoyl]-L-threonine (t2G) and N-[(1-beta-D-ribofuranosyl-2-oxypyrimidin-4-yl)carbamoyl]-L-threonine (t4C), were prepared. Also synthesized were the corresponding glycine analogs, g2G and g4C, from guanosine and cytidine, respectively. The 2'-deoxyribosyl analog, N-[(9-beta-D-2'-deoxyribofuranosylpurin-6-yl)carbamoyl]-L-threonine (2'-deoxy-t6A), and the arabinosyl derivative, N-[(9-beta-D-arabinofuranosylpurin-6-yl)carbamoyl]-L-threonine (t6AraA), were synthesized from the appropriate urethane and the requisite amino acid. The ureido group in mt6A could not be hydrolyzed by the enzymes urease, peptidase, and protease. Various chemical and biological properties of the naturally occurring mt6A and the related analogs are discussed.
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PMID:Synthesis properties of the naturally occurring N-[(9-beta-D-ribofuranosylpurin-6-yl)-N-methylcarbamoyl]-L-threonine (mt-6A) and other related synthetic analogs. 114 94

Acid urease was purified to an electrophoretically homogeneous state, and the molecular weight was estimated to be 220,000. The enzyme consisted of three kinds of subunits, designated alpha, beta and gamma, with molecular weights of 67,000, 16,800 and 8600, respectively, in a (alpha 1 beta 2 gamma 1)2 structure. The isoelectric point of the enzyme was 4.8. The nickel content was found to be 1.9 atoms of nickel per alpha 1 beta 2 gamma 1 unit. The amino acid profile was different from those of known bacterial neutral ureases. The enzyme was most active at pH 2 and around 65 degrees C. It was stable between pH 3 and 9, and below 50 degrees C. The Km for urea was 2.7 mM at pH 2. The enzyme activity was inhibited by Ag+, Hg2+, Cu2+, p-chloromercuribenzoate and acetohydroxamate. The enzyme was separated into three subunits by reverse phase HPLC. The amino terminal amino acid sequences of the subunits alpha, beta and gamma were Ser-Phe-Asp-Met-, Met-Val-Pro-Gly- and Met-Arg-Leu-Thr-, respectively.
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PMID:Purification and characterization of acid urease from Lactobacillus fermentum. 136 38

The nucleotide sequences of the complete set of tRNA species in Mycoplasma capricolum, a derivative of Gram-positive eubacteria, have been determined. This bacterium represents the first genetic system in which the sequences of all the tRNA species have been determined at the RNA level. There are 29 tRNA species: three for Leu, two each for Arg, Ile, Lys, Met, Ser, Thr and Trp, and one each for the other 12 amino acids as judged from aminoacylation and the anticodon nucleotide sequences. The number of tRNA species is the smallest among all known genetic systems except for mitochondria. The tRNA anticodon sequences have revealed several features characteristic of M. capricolum. (1) There is only one tRNA species each for Ala, Gly, Leu, Pro, Ser and Val family boxes (4-codon boxes), and these tRNAs all have an unmodified U residue at the first position of the anticodon. (2) There are two tRNAThr species having anticodons UGU and AGU; the first positions of these anticodons are unmodified. (3) There is only one tRNA with anticodon ICG in the Arg family box (CGN); this tRNA can translate codons CGU, CGC and CGA. No tRNA capable of translating codon CGG has been detected, suggesting that CGG is an unassigned codon in this bacterium. (4) A tRNATrp with anticodon UCA is present, and reads codon UGA as Trp. On the basis of these and other observations, novel codon recognition patterns in M. capricolum are proposed. A comparatively small total, 13, of modified nucleosides is contained in all M. capricolum tRNAs. The 5' end nucleoside of the T psi C-loop (position 54) of all tRNAs is uridine, not modified to ribothymidine. The anticodon composition, and hence codon recognition patterns, of M. capricolum tRNAs resemble those of mitochondrial tRNAs.
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PMID:Codon recognition patterns as deduced from sequences of the complete set of transfer RNA species in Mycoplasma capricolum. Resemblance to mitochondria. 247 13

The levels of several enzymes involved in assimilation of different nitrogen compounds were investigated in Streptomyces clavuligerus in relation to the nitrogen source supplied to the cultures. Threonine dehydratase, serine dehydratase, proline dehydrogenase, histidase and urocanase were not decreased in the presence of ammonium. The latter two enzymes were induced by histidine in the culture medium, while proline dehydrogenase was induced by proline. Glutamine synthetase, urease and ornithine aminotransferase levels were higher with poor nitrogen sources and were repressed by ammonium. Arginase was induced by arginine and repressed by ammonium. Glutamine synthetase was rapidly inactivated upon addition of ammonium to the culture, and could be reactivated in vitro by treatment with snake venom phosphodiesterase, which suggested that adenylylation is involved in the inactivation. Three previously isolated mutants with abnormal glutamine synthetase activities showed pleiotropic effects on urease formation. All these data point to a mechanism controlling preferential utilization of some nitrogen sources in this species.
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PMID:Regulation of nitrogen catabolic enzymes in Streptomyces clavuligerus. 257 37

Increased brain and plasma glutamine after ammonia inhalation had an effect on the concentrations of selected amino acids in rats. Rats inhaled ammonia vapour of 25 and 300 p.p.m. for 5 days 6 hr daily. Brain glutamine increased from the control level, 10.9 +/- 2.6 (S.D.) mumol/g to 15.5 +/- 5.2 (S.D.) mumol/g (P less than 0.05) in 25 p.p.m. NH3 and to 15.3 +/- 1.1 (S.D.) mumol/g (P less than 0.01) in 300 p.p.m. NH3. The blood glutamine was also increased so that the brain/plasma ratio was not changed. A slight elevation in the brain threonine was found, from 0.6 +/- 0.1 (S.D.) mumol/g (controls) to 0.8 +/- 0.2 (S.D.) mumol/g in 25 p.p.m. and to 0.8 +/- 0.1 (S.D.) mumol/g in 300 p.p.m. NH3. The brain/plasma ratio of threonine was increased at the 300 p.p.m. level. The increasing brain threonine linearly correlated to the increased plasma glutamine the general correlation co-efficient being 0.59 according to a linear regression analysis. The effects on other amino acids, e.g., glycine, alanine, serine, aspartate, glutamate, were less clear. It seems that the elevated blood glutamine impaired the threonine export or augmented its uptake from the blood stream. Exposure to NH3 vapour by inhalation proved to be an alternative model to portocaval shunting or urease injections in the study of hyperammonemia in the brain.
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PMID:Effect of short-term ammonia inhalation on selected amino acids in rat brain. 272 87

1. Yeast alcohol dehydrogenase was used to determine ethanol in the portal and hepatic veins and in the contents of the alimentary canal of rats given a diet free from ethanol. Measurable amounts of a substance behaving like ethanol were found. Its rate of interaction with yeast alcohol dehydrogenase and its volatility indicate that the substance measured was in fact ethanol. 2. The mean alcohol concentration in the portal blood of normal rats was 0.045mm. In the hepatic vein, inferior vena cava and aorta it was about 15 times lower. 3. The contents of all sections of the alimentary canal contained measurable amounts of ethanol. The highest values (average 3.7mm) were found in the stomach. 4. Infusion of pyrazole (an inhibitor of alcohol dehydrogenase) raised the alcohol concentration in the portal vein 10-fold and almost removed the difference between portal and hepatic venous blood. 5. Addition of antibiotics to the food diminished the ethanol concentration of the portal blood to less than one-quarter and that of the stomach contents to less than one-fortieth. 6. The concentration of alcohol in the alimentary canal and in the portal blood of germ-free rats was much decreased, to less than one-tenth in the alimentary canal and to one-third in the portal blood, but detectable quantities remained. These are likely to arise from acetaldehyde formed by the normal pathways of degradation of threonine, deoxyribose phosphate and beta-alanine. 7. The results indicate that significant amounts of alcohol are normally formed in the gastro-intestinal tract. The alcohol is absorbed into the circulation and almost quantitatively removed by the liver. Thus the function, or a major function, of liver alcohol dehydrogenase is the detoxication of ethanol normally present. 8. The alcohol concentration in the stomach of alloxan-diabetic rats was increased about 8-fold. 9. The activity of liver alcohol dehydrogenase is generally lower in carnivores than in herbivores and omnivores, but there is no strict parallelism between the capacity of liver alcohol dehydrogenase and dietary habit. 10. The activity of alcohol dehydrogenase of gastric mucosa was much decreased in two out of the three germ-free rats tested. This is taken to indicate that the enzyme, like gastric urease, may be of microbial origin. 11. When the body was flooded with ethanol by the addition of 10% ethanol to the drinking water the alcohol concentration in the portal vein rose to 15mm and only a few percent of the incoming ethanol was cleared by the liver.
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PMID:The physiological role of liver alcohol dehydrogenase. 548 98

Cysteine residues in the active center of jack bean urease [EC 3.5.1.5] were modified with 14C-labeled diazonium-1H-tetrazole (DHT). The labeled enzyme was carboxymethylated with iodoacetic acid, and then hydrolyzed with trypsin. The tryptic digest was subjected to gel filtration on Sephadex G-50, yielding two radioactive fractions. The [14C]DHT-labeled peptide having a lower molecular weight, which was determined to be approximately 1,000 by the method of gel filtration, was further purified to homogeneity by ion-exchange chromatography on DEAE-Sephadex A-25. [14C]DHT-labeled cysteine was identified as cysteic acid after performic acid oxidation, and the amino acid sequence of the low-molecular-weight [14C]DHT-labeled peptide was determined to be Phe-Glu-Pro-Gly-Asp-Cys-Asn-Ser-Thr-Phe-Lys.
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PMID:Amino acid sequence around a cysteine residue in the active center of jack bean urease. 649 Jun 9

To examine the rate-of-living theory, age-related changes in amino acid pool sizes were investigated in the adult silkmoth, Bombyx mori, reared at low and high temperature. At either temperature concentrations of free amino acids contained in silkmoths revealed a great sexual difference. Those in females were generally much higher than in males and the former changed much more dynamically than the latter. Major amino acids or ninhydrin-positive compounds inclusive of some essential amino acids such as Leu, Ile, Val, Thr, Arg, Phe, Met, Ala, Tyr, Gln, Aspn , Lan , Cysta , GABA and PEA accumulated in 4 degrees C-moths. However, the levels of these amino changed irregularly with advanced age. Inhibition of protein synthesis may occur generally at low temperature, while protein degradation may be promoted at high temperature. High concentrations of MSO and Tau in the moths reared at high temperature than in the normal moths suggested also catabolism of amino acids proceeding together with protein degradation at high temperature. Amino acid metabolism seems to be complicated under various temperature conditions. When reared at the optimal temperature of 25 degrees C, urea is not present in the body of the silkmoth except for a slight amount in the secreted meconium. In silkmoths reared at the higher temperature of 35 degrees C, however, an extraordinary accumulation of urea occurs accompanied by a reduction in lifespan by one half. Undoubtedly, urea is produced in this terrestrial insect, although the accumulation mechanism is not clear: in silkmoths reared at various temperatures, arginase is found, but urease is not detected. Arginase activity was found to be higher in male moths than in female moths regardless of the rearing temperature. High temperature rearing also did not induce activity and female activity never exceeded that in males at either 25 degrees C or 35 degrees C rearing. Protein degradation accelerated by rearing at high temperatures may result in increased amounts of free arginine, which could cause the active production of urea. This possibility would be a counter-argument to the rate of living theory relating to longevity and temperature. However, at least the above facts signify that an extrinsic factor influences the longevity of an animal by altering its intrinsic aging process.
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PMID:Age-related changes in amino acid pool sizes in the adult silkmoth, Bombyx mori, reared at low and high temperature; a biochemical examination of the rate-of-living theory and urea accumulation when reared at high temperature. 672 18

A gram-negative, anaerobic, nonmotile, non-spore-forming, rod-shaped bacterium that fermented succinate quantitatively to propionate was isolated from a high dilution of rumen ingesta obtained from a dairy cow fed a production diet containing grass silage as the main roughage source. This organism did not grow on any of the following energy sources: 12 carbohydrates, pyruvate, lactate, 7 dicarboxylic acids, aspartate, citrate, and trans-aconitate. Both rumen fluid and yeast extract were necessary for good growth on succinate. The organism was negative for the following characteristics: production of propionate from threonine, protein digestion, sulfide production, nitrate reduction, catalase activity, and urease activity. There was no growth at 22 degrees C and reduced growth at 45 degrees C compared with growth at 39 degrees C. The DNA base composition was 52 mol% G + C. The complete 16S rRNA sequence (EMBL accession number, X81137) was obtained, and the phylogenetic relationships of the organism were determined. The most closely related genera were the genera Acidaminococcus and Phascolarctobacterium. The name proposed for this bacterium is Succiniclasticum ruminis gen. nov., sp. nov.; the type strain is strain SE10 (= DSM 9236). Additional isolation attempts revealed that S. ruminis is a common inhabitant of the rumina of cows that are fed production diets and of cows on pasture.
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PMID:Succiniclasticum ruminis gen. nov., sp. nov., a ruminal bacterium converting succinate to propionate as the sole energy-yielding mechanism. 753 62


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