Gene/Protein Disease Symptom Drug Enzyme Compound
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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)

The toxicity of Cu, Ni and Fe individually, as well as in combination (Cu + Ni, Cu + Fe, Ni + Fe), on growth-rate depression, uptake of NO3- and NH4+, photosynthesis, nitrate reductase and urease activity of Chlorella vulgaris has been studied. All the test metals when used individually showed pronounced toxicity on all the parameters studied. However, their interactive effect was mostly antagonistic except for Cu + Ni (synergism). Pre-addition of Fe offered more protection to the cells against copper and nickel toxicity. The data of statistical analysis reconfirmed that 14CO2 uptake is the most sensitive parameter (significant at P less than 0.005, both for time and treatment) than others in metal toxicity assessment. However, these results suggest further that exposure time and sequence of metal addition are very important in biomonitoring of heavy metal toxicity.
Biol Met 1990
PMID:Impact of bimetallic combinations of Cu, Ni and Fe on growth rate, uptake of nitrate and ammonium, 14CO2 fixation, nitrate reductase and urease activity of Chlorella vulgaris. 216 14

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

Brain ammonia is generated from many enzymatic reactions, including glutaminase, glutamate dehydrogenase, and the purine nucleotide cycle. In contrast, the brain possesses only one major enzyme for the removal of exogenous ammonia, i.e., glutamine synthetase. Thus, following administration of [13N]ammonia to rats [via either the carotid artery or cerebrospinal fluid (csf)], most metabolized label was in glutamine (amide) and little was in glutamate (plus aspartate). Since blood-and csf-borne ammonia are converted to glutamine largely, if not entirely, in the astrocytes, it is not possible from these types of experiments to predict with certainty the metabolic fate of the bulk of endogenously produced ammonia. By comparing the specific activity of L-[13N]glutamate to that of L-[amine-13N]glutamine following intracarotid [13N]ammonia administration it was concluded that metabolic compartmentation is no longer intact in the brains of rats treated with the glutamine synthetase inhibitor L-methionine-SR-sulfoximine (MSO) and that blood and brain ammonia pools mix in such animals. In MSO-treated animals, recovery of label in brain was low (approximately 20% of controls), and of the label remaining, a prominent portion was in glutamine (amide) (despite an 87% decrease in brain glutamine synthetase activity). These data are consistent with the hypothesis that glutamine synthetase is the major enzyme for metabolism of endogenously--as well as exogenously--produced ammonia. The rate of turnover of blood-derived ammonia to glutamine in normal rat brain is extremely rapid (t1/2 less than or equal to 3 s), but is slowed in the brains of chronically (12-14-wk portacaval-shunted) or acutely (urease-treated) hyperammonemic rats (t1/2 less than or equal to 10 s). The slowed turnover rate may be caused by an increased astrocytic ammonia, decreased glutamine synthetase activity, or both. In the hyperammonemic rat brain, glutamine synthetase is still the only important enzyme for the removal of blood-borne ammonia. Hyperammonemia causes an increase in brain lactate/pyruvate ratios and decreases in brain glutamate and brainstem ATP, consistent with an interference with the malate-aspartate shuttle. In vitro, pathological levels of ammonia also inhibit brain alpha-ketoglutarate dehydrogenase complex and, less strongly, pyruvate dehydrogenase complex. The rat brain does not adapt to prolonged hyperammonemia by increasing its glutamine synthetase activity.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Cerebral ammonia metabolism in normal and hyperammonemic rats. 288 66

Colony counts of fecal samples from three persons, obtained by using a chemically defined anaerobic roll-tube medium (containing glucose, maltose, glycerol, minerals, hemin, B-vitamins, methionine, volatile fatty acids, sulfide, bicarbonate, agar, carbon dioxide (gas phase), and 1 mM NH(4) (+) as main nitrogen source), averaged 60% of the 8.8 x 10(10) bacteria per g obtained when 0.2% Trypticase and 0.05% yeast extract were added to the otherwise identical medium. When 0.2% vitamin-free Casitone replaced Trypticase and yeast extract, counts were 94% those of the more complex medium. When urea-nitrogen was added to the defined medium as the main nitrogen source in place of NH(4) (+), counts of relatively large colonies averaged 1.0 x 10(9) per g of feces from five persons-1.1% of counts on the medium containing Trypticase and yeast extract. All of the organisms from the large colonies in the urea roll tubes were morphologically similar, and all six representative strains isolated were identified as urease-forming Peptostreptococcus productus, a species not previously known to produce urease. Ureolytic strains of Selenomonas ruminantium and P. productus were negative for urease activity in three assay media when inocula were from media containing complex nitrogen sources. The study documents that P. productus is the most numerous ureolytic species so far found in human feces and suggests that NH(4) (+) and more complex organic nitrogen sources strongly repress its production of urease. The study also indicates the efficacy of chemically defined media for direct selective isolation of nutritional groups of bacteria from feces.
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PMID:Isolation of ureolytic Peptostreptococcus productus from feces using defined medium; failure of common urease tests. 421 72

To determine the most useful diagnostic characters for the differentiation of pseudomonads pathogenic for man, including Pseudomonas maltophilia (Alcaligenes bookeri), P. stutzeri (Bacillus denitrificans), P. pseudomallei (Malleomyces pseudomallei), and apyocyanogenic strains of P. aeruginosa, a comparative examination was made of 58 strains of these bacilli for their morphological and biochemical characteristics. It was concluded that the criteria for differentiating these bacteria are type of flagellation, growth on S S Agar, fluorescein production, oxidation of carbohydrates in the medium of Hugh and Leifson, nitrogen gas production, gluconate oxidation, gelatinase activity, urease activity, lysine decarboxylase activity, arginine dihydrolase activity, oxidase reaction, sensitivity to polymyxin, requirement for methionine as a growth factor, and assimilation of organic compounds as the sole source of carbon and energy.
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PMID:Diagnostic criteria for differentiation of pseudomonads pathogenic for man. 487 13

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.
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PMID:The subunit structure of jack-bean urease. 538 87

Urease and glutamine synthetase activities in Selenomonas ruminantium strain D were highest in cells grown in ammonia-limited, linear-growth cultures or when certain compounds other than ammonia served as the nitrogen source and limited the growth rate in batch cultures. Glutamate dehydrogenase activity was highest during glucose (energy)-limited growth or when ammonia was not growth limiting. A positive correlation (R = 0.96) between glutamine synthetase and urease activities was observed for a variety of growth conditions, and both enzyme activities were simultaneously repressed when excess ammonia was added to ammonia-limited, linear-growth cultures. The glutamate analog methionine sulfoximine (MSX), inhibited glutamine synthetase activity in vitro, but glutamate dehydrogenase, glutamate synthase, and urease activities were not affected. The addition of MSX (0.1 to 100 mM) to cultures growing with 20 mM ammonia resulted in growth rate inhibition that was dependent upon the concentration of MSX and was overcome by glutamine addition. Urease activity in MSX-inhibited cultures was increased significantly, suggesting that ammonia was not the direct repressor of urease activity. In ammonia-limited, linear-growth cultures, MSX addition resulted in growth inhibition, a decrease in GS activity, and an increase in urease activity. These results are discussed with respect to the importance of glutamine synthetase and glutamate dehydrogenase for ammonia assimilation under different growth conditions and the relationship of these enzymes to urease.
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PMID:Regulation of urease and ammonia assimilatory enzymes in Selenomonas ruminantium. 611 7

1. Using the isolated perfused lung preparation we have demonstrated a low-activity ureolytic enzyme present in rodent lung tissue. The enzyme shares four characteristic features with jack bean urease (EC 3.5.1.5). 2. Ureolytic activity was inhibited by fluoride ions and methionine hydroxamic acid; using the latter inhibitor, the I50 value and maximum inhibition were similar to those reported for jack bean urease. The apparent Km for rat lung urease was similar to the plasma urea level. 3. The low level of urease activity in the rat lung and in that of Notomys alexis, a desert rodent, suggests that the enzyme is not involved in urea excretion, rather that pulmonary ammonia production may influence fluid balance at the alveolus.
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PMID:Urea metabolism in isolated perfused lungs of the laboratory rat and of a desert rodent, Notomys alexis. 613 90

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

Photo-oxidation of Jack bean urease was performed in the presence of a low concentration of methylene blue, which led to the complete loss of the enzymatic activity. The inactivation was more remarkable in an alkaline region than in an acidic region and prevented by the addition of histidine or methionine. Amino acid analysis of the oxidized enzyme revealed that the number of histidine residues had decreased to 73% that of the native enzyme, but the numbers of other amino acid residues were not significantly affected. Benzohydroxamic acid, a specific urease inhibitor, protected the active site of the enzyme against photo-oxidation. On the other hand, oxidation of the enzyme decreased its binding ability with caprylo- and benzohydroxamic acid to one-third. These results suggest that histidine residues are modified by photo-oxidation and are essential to both the enzymatic activity and the binding ability with hydroxamic acid.
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PMID:Photo-oxidation of Jack bean urease in the presence of methylene blue. 687 59


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