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)

This communication presents evidence from the literature and recent experiments that describe circumstances wherein arginine may be a conditional dietary essential. Previous work has established that the synthesis of orotic acid (OA), the first pyrimidine formed in the de novo pathway of nucleic acid synthesis, becomes elevated whenever the ammonia load exceeds the capacity of the urea cycle. Under these circumstances, the common intermediate, carbamyl phosphate, leaks from the mitochondria and induces OA synthesis in the cytoplasm. This leads to increased OA excretion in the urine as pyrimidine synthesis escapes feedback control. A deficiency of urea cycle substrates such as arginine, and administration of certain drugs, ammonium salts, urease, or excess amino acids raises orotic acid excretion. Our recent experiments in rats show that OA excretion is also elevated after partial hepatectomy following galactosamine administration, exposure to carbon tetrachloride, or feeding 36% of calories as ethanol. The elevation in OA excretion was suppressed by dietary supplementation with arginine, implying that arginine is conditionally essential. Adult human male alcoholics showed elevated urinary orotic acid-to-creatinine ratios early after drinking episodes, which declined with time following abstinence. Such evidence shows that well studied hepatotoxins and surgical liver injury affect pathways of ammonia metabolism and suggests that urinary orotic acid can be an indicator of hepatotoxicity and increased needs for arginine. Arginine-deficient diets and alcohol feeding both enhance fatty deposition in the liver, which can be worsened by high fat intakes in rats. Alcoholism, various other diseases, and fasting and realimentation change orotic acid excretion. Such responses will have to be taken into account in establishing "normal values" for OA excretion.
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PMID:Orotic acid, arginine, and hepatotoxicity. 352 4

Five polyamines which could be separated by high performance liquid chromatography were found in Acanthamoeba castellanii (strain Neff). These included in order of decreasing abundance: 1,3-diaminopropane, spermidine, spermine, norspermidine, and putrescine. Only diaminopropane and norspermidine had been found previously. Spermine was present in cultures grown in broth, but not in defined medium. Radioactive substrates were used to establish that putrescine was synthesized by decarboxylation of ornithine, ornithine was synthesized from arginine or citrulline, and diaminopropane was synthesized from spermidine. The presence of ornithine decarboxylase (EC 4.1.1.17), arginase (EC 3.5.3.1), and urease (EC 3.5.1.5) and the absence of arginine decarboxylase (EC 4.1.1.19) were established. A scheme for polyamine biosynthesis in A. castellanii is proposed.
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PMID:Polyamine metabolism in Acanthamoeba: polyamine content and synthesis of ornithine, putrescine, and diaminopropane. 365 16

A sensitive colorimetric assay for arginase was developed. Urea produced by arginase was hydrolyzed to ammonia by urease, the ammonia was converted to indophenol, and the absorbance was measured at 570 nm. The assay is useful with low concentrations of arginase (0.5 munit or less than 1 ng rat liver arginase) and with a wide range of arginine concentrations (50 microM to 12.5 mM). Michaelis-Menten kinetics and a Km for arginine of 1.7 mM were obtained for Mn2+-activated rat liver arginase; the unactivated enzyme did not display linear behavior on double-reciprocal plots. The kinetic data for unactivated arginase indicated either negative cooperativity or two types of active sites on the arginase tetramer with different affinities for arginine. The new assay is particularly well suited for kinetic studies of activated and unactivated arginase.
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PMID:Assay and kinetics of arginase. 372 59

Ureaplasma urealyticum lacks the conventional mechanisms for adenosine 5-triphosphate (ATP) generation, such as glycolysis or arginine breakdown, present in other mycoplasmas. The possibility that ATP may be generated in these organisms through the formation of an ion gradient coupled to urea hydrolysis has been suggested by Masover and Hayflick (Ann NY Acad Sci 225:118-130, 1973). Our data have proved that ATP is produced when urea is added to resting ureaplasmal cells and its formation requires the concomitant activity of both cytoplasmic urease and membrane-bound ATPase and is drastically reduced by carbonylcyanide-m-chlorophenylhydrazine. Analysis of the optimal conditions for ATP synthesis in ureaplasmas indicates that this energetic process depends upon phosphate, urea, pH and ammonium ions in the reaction mixture. Particularly ammonium ions can interfere with the production of energy only when the starting pH is kept slightly basic. We have also shown that the changes in fluorescence intensity are directly related to the concentrations of the added urea and are inhibited by the presence of acetohydroxamic acid, carbonycyanide-m-chlorophenylhydrazine, and ammonium ions. It appears that urea hydrolysis can generate an electrical potential through NH4+ diffusion across the Ureaplasma membranes, but this diffusion is also dependent upon the external acidic pH of the reaction mixture.
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PMID:Energy production in Ureaplasma urealyticum. 379 30

As the present classification (19) of Clostridium sordellii and C. bifermentans is based on properties which are not conclusive for most of our strains, we investigated 80 strains from various origin of this group regarding 30 selected properties. Four of these properties were correlative and therefore particularly important for a distinct differentiation of the strains investigated: urease activity (U), growth inhibition by 1% mannose (M), arginine deaminase activity (A), and sialidase (EC 3.2.1.18) activity (S). Concerning these four characters three clusters were formed: cluster I was positive for U, M, A, and S and comprised 36 strains including C. sordellii type strain (ATCC 9714T); cluster II was positive for M and S and negative for U and A and comprised twelve strains including strain ATCC 35392; and cluster III was positive for A and negative for U, M, and S and comprised 32 strains including C. bifermentans type strain (ATCC 638T). Only two of the correlative properties (U and S, U and A, A and M, or A and S) needed to be tested to determine the affiliation of any strain of the C. sordellii/bifermentans group to one of the three clusters. Clusters I and II, representing two phenotypes of C. sordellii, can now clearly be distinguished from C. bifermentans. Sialidase formed by cluster I and II strains was inhibited by antibodies produced against cluster I strain sialidase. No cross reaction was found with other clostridial sialidases. Pathogenicity, hitherto considered as one of the distinctive properties of C. sordellii and C. bifermentans, was found with various strains of all the three clusters. Therefore, in the case of an infection caused by these two species, care should be taken as to the pathogenicity especially of C. bifermentans and treatment should be accordingly.
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PMID:Correlative properties for a differentiation of two Clostridium sordellii phenotypes and their distinction from Clostridium bifermentans. 391 62

We present a study of the enzymatic activities involved in the pathway for arginine catabolism by Agrobacterium tumefaciens. Nitrogen from arginine is recovered through the arginase-urease pathway; the genes for these two activities are probably chromosomally born. Arginase was found to be inducible during growth in the presence of arginine or ornithine. Urease was constitutively expressed. Ornithine, resulting from the action of arginase on arginine, could be used as a nitrogen source via transamination to delta 1-pyrroline-5-carboxylate and reduction of the latter compound to proline by a reductase (both enzymatic activities are probably chromosomally encoded). Ornithine could also be used as a carbon source. Thus, we identified an ornithine cyclase activity that was responsible for direct conversion of ornithine to proline. This activity was found to be Ti plasmid encoded and inducible by growth in medium containing octopine or nopaline. The same activity was also chromosomally encoded in some Agrobacterium strains. In such strains, this activity was inducible during growth in arginine-containing medium.
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PMID:Arginine catabolism in Agrobacterium strains: role of the Ti plasmid. 395 72

The fastidious growth requirements of mycoplasmas and ureaplasmas necessitated development of special growth media for them. The 1st mycoplasma was isolated from humans in 1937, and in 1954 a previously unknown mycoplasma was isolated from men with nonspecific urethritis. This organism, Ureaplasma urealyticum, is found most frequently in the genitourinary tract, followed by Mycoplasma hominus. M. fermentans and other mycoplasmas are isolated only rarely. Mycoplasmas and ureaplasmas have been implicated in pelvic inflammatory disease, puerperal infection, septic abortion, low birth weight, nongonococcal urethritis, and prostatisis, as well as spontaneous abortion and infertility, but there are no clinical symptoms pathognomonic of these infections. In spite of clinical suggestions of Mycoplasma or Ureaplasma infection, only a properly obtained specimen evaluatd with the use of selective cultures can lead to unequivocal diagnosis. The cultural characteristics and hence diagnostic procedures for Mycoplasma and Ureaplasma are quite different. Sterile calcium alginate swabs are used for obtaining urethral specimens, while sterile cotton swabs can be used for prostatic or vaginal secretions or semen. The swab should not touch antiseptic solutions, creams, or jellies, and the specimen must not dry out. Urine, if cultured, is best examined after centrifugattion at 600 g. Several different transport media are available. Optimally the specimen should be taken directly to the laboratory and subcultured on arrival. The metabolic activity of Mycoplasmas and Ureaplasmas is used in their detection. A phenol red indicator is added to the medium and the color change to or from yellow to pink indicates metabolic change. The growth medium is supplemented with glucose and phenol red for M. fermentans and arginine and phenol red for M. hominis. After color change is observed, the growth medium is subcultured on solid medium, which is obtained by adding .6-.8% Noble agar to the growth medium. Colonies develop best in an atmosphere of 95% N2 and 5% CO2 and reach approximately 200-300 mcm in diameter. They have a fried-egg appearance. Staining with Dienes stain, use of specific antisera, or incident light fluorescence microscopy are used for identification of the classic mycoplasmas. To isolate ureaplasmas, the specimen is transferred on arrival in the laboratory to urease color test broth U9C. During incubation the presence of Ureaplasma induces a rapid color change usually observable in 24-48 hours. A subculture should be done on fresh U9C broth media and on agar media once a color change is observed. Serologic tests for detection of antibodies to mycoplasmas and ureaplasmas are still in the developmental stage.
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PMID:Diagnosis of genital Mycoplasma and Ureaplasma infections. 402 Jul 82

Cultures of Escherichia coli B and K-12 produce urea during growth in minimal medium. Results of isotopic labeling experiments were consistent with the sole source of urea being from the conversion of arginine to putrescine. Since E. coli itself has no demonstrable urease activity, the rate of urea production is a measure of the flux through the arginine to putrescine pathway.
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PMID:Urea production and putrescine biosynthesis by Escherichia coli. 486 95

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

The pathway of arginine biosynthesis in Streptococcus bovis was studied by radioactive tracer techniques. Cells were grown anaerobically with (14)CO(2) in a synthetic medium containing NH(4) (+) as the sole nitrogen source except for the trace present in nitrogen-containing vitamins. The protein fraction isolated from the labeled cells was acid-hydrolyzed, and (14)C-arginine was isolated from the protein hydrolysate by ion-exchange chromatography. The carboxyl carbon of the isolated arginine was removed with arginine decarboxylase, and the guanidino carbon was removed by simultaneous arginase-urease degradation. By manometric measurement and liquid scintillation counting of the CO(2) released by enzymatic degradation, 50% of the label was found in the carboxyl carbon and 50% in the guanidino carbon. Specific radioactivity determinations indicated that growth on (14)CO(2) resulted in twice as much label in arginine as with aspartate, glutamate, or lysine. These results are consistent with a glutamate --> ornithine --> citrulline pathway of arginine biosynthesis in S. bovis and provide further evidence for the synthesis of glutamate via the tricarboxylic acid cycle reactions from citrate through alpha-ketoglutarate.
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PMID:Arginine biosynthesis by Streptococcus bovis. 605 38


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