Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

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

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

1. Portacaval shunting in rats results in several metabolic alterations similar to those seen in patients with hepatic encephalopathy. The characteristic changes include: (a) diminution of cerebral function; (b) raised plasma ammonia and brain glutamine levels; (c) increased neutral amino acid transport across the blood-brain barrier; (d) altered brain and plasma amino acid levels; and (e) changes in brain neurotransmitter content. The aetiology of these abnormalities remains unknown. 2. To study the degree to which ammonia could be responsible, rats were made hyperammonaemic by administering 40 units of urease/kg body weight every 12 h and killing the rats 48 h after the first injection. 3. The changes observed in the urease-treated rats were: (a) whole-brain glucose use was significantly depressed, whereas the levels of high-energy phosphates remained unchanged; (b) the permeability of the blood-brain to barrier to two large neutral amino acids, tryptophan and leucine, was increased; (c) blood-brain barrier integrity was maintained, as indicated by the unchanged permeability-to-surface-area product for acetate; (d) plasma and brain amino acid concentrations were altered; and (e) dopamine, 5-hydroxytryptamine (serotonin) and noradrenaline levels in brain were unchanged, but 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of 5-hydroxytryptamine, was elevated. 4. The depressed brain glucose use, increased tryptophan permeability-to-surface-area product, elevated brain tryptophan content and rise in the level of cerebral 5-HIAA were closely correlated with the observed rise in brain glutamine content. 5. These results suggest that many of the metabolic alterations seen in rats with portacaval shunts could be due to elevated ammonia levels. Furthermore, the synthesis or accumulation of glutamine may be closely linked to cerebral dysfunction in hyperammonaemia.
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PMID:Hyperammonaemia causes many of the changes found after portacaval shunting. 170 23

RNA editing, a process that results in the production of RNA molecules having a nucleotide sequence different from that of the initial DNA template, has been demonstrated in several organisms using different biochemical pathways. Very recently RNA editing was described in plant mitochondria following the discovery that the sequence of certain wheat and Oenothera cDNAs is different from the nucleotide sequence of the corresponding genes. The main conversion observed was C to U, leading to amino acid changes in the deduced protein sequence when these modifications occurred in an open reading frame. In this communication we show the first attempt to isolate and sequence a protein encoded by a plant mitochondrial gene. Subunit 9 of the wheat mitochondrial ATP synthase complex was purified to apparent homogeneity and the sequence of the first 32 amino acid residues was determined. We have observed that at position 7 leucine was obtained by protein sequencing, instead of the serine predicted from the previously determined genomic sequence. Also we found phenylalanine at position 28 instead of a leucine residue. Both amino acid conversions, UCA (serine) to UUA (leucine) and CUC (leucine) to UUC (phenylalanine), imply a C to U change. Thus our results seem to confirm, at the protein level, the RNA editing process in plant mitochondria.
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PMID:Direct protein sequencing of wheat mitochondrial ATP synthase subunit 9 confirms RNA editing in plants. 219 74

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 effects of oral and intraperitoneal administration of biotin in urease-induced hyperammonemic rats, as well as the influence of biotin deficiency, have been studied. Biotin deficiency was produced by feeding standard diet MF (Oriental Yeast Co.) supplemented with dry egg-white (egg-white group). Egg-white + biotin group had free access to 0.0014% of biotin solution at all time. Following an intraperitoneal injection of urease, 25 U/kg (B.W.), plasma ammonia levels in egg-white + biotin group were lower than in egg-white group, especially there was significance (p less than 0.05) at 8 hours after the urease injection. Similarly, plasma ammonia levels in biotin-injected rats, in which 1 mg of biotin had been injected intraperitoneally prior to the experiment, were significantly low compared with saline-injected controls at 4 and 6 hours after urease administration. Results of plasma amino acid analysis, 9 hours after the urease injection indicated that Fischer's molar ratio (Leu + Ileu + Val/Tyr + Phe) was significantly higher in the biotin-injected rats than the saline-injected control. It suggests that biotin might decrease blood ammonia by facilitating the detoxification mechanism as follow: L-glutamate + NH3----L-glutamine.
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PMID:[The effects of biotin on the metabolism of ammonia and amino acids in urease-induced hyperammonemic rats]. 281 Aug 55

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

We have investigated the molecular basis for a deficiency of the enzyme hypoxanthine (guanine) phosphoribosyltransferase (HPRT; IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) in a patient with a severe form of gout. We reported in previous studies the isolation of a unique structural variant of HPRT from this patient's erythrocytes and cultured lymphoblasts. This enzyme variant, which is called HPRTLondon, is characterized by a decreased concentration of HPRT protein in erythrocytes and lymphoblasts, a normal Vmax, a 5-fold increased Km for hypoxanthine, a normal isoelectric point, and an apparently smaller subunit molecular weight. Comparative peptide mapping experiments revealed a single abnormal tryptic peptide in HPRTLondon. Edman degradation of the aberrant peptide from HPRTLondon identified a serine-to-leucine amino acid substitution at position 109. This substitution can be explained by a single nucleotide change in the codon for serine-109 (UCA leads to UUA). Thus a mutation at the HPRT locus has now been defined at the molecular level.
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PMID:Human hypoxanthine (guanine) phosphoribosyltransferase: an amino acid substitution in a mutant form of the enzyme isolated from a patient with gout. 657 73

We have cloned and sequenced the wild-type and suppressor alleles of the S. pombe sup8 tRNA gene. The wild-type allele has a leucine UAA anticodon and the suppressor (sup8-e) carries the opal suppressor anticodon UCA. The gene has a 16 base pair intervening sequence that, in the RNA, is predicted to form a secondary structure which involves base pairing to the 5', rather than the usual 3' side of the 5' splice site. When incubated in Saccharomyces cerevisiae cell-free extracts both alleles are efficiently transcribed, the 5' leader and 3' trailer sequences are removed and CCA is added to the 3' processed end; however, the intervening sequence is not excised. This finding implies that the structural requirements of the splicing endonucleases in the two yeasts have diverged. No other tRNA genes with related sequences were detected in S. pombe DNA by hybridization, suggesting that other UUA isoacceptors may be structurally dissimilar to sup8 or that the UUA codon may be decoded by a UUG leucine isoacceptor.
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PMID:The sup8 tRNALeu gene of Schizosaccharomyces pombe has an unusual intervening sequence and reduced pairing in the anticodon stem. 659 38

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


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