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)

We describe a new stable isotope technique for the in vivo study of hepatic plasma protein synthesis in humans. The method involves the infusion of (13C)sodium bicarbonate for 1 h and the measurement of the isotopic enrichment of (13C)arginine in newly synthesized apolipoprotein B of very low density lipoproteins (VLDL-apoB) and low density lipoproteins (LDL-apoB) in blood samples taken over a 5-6 h period from the commencement of the infusion. Isotope ratio mass spectrometry was utilized to measure 13CO2 enrichment following hydrolysis of these proteins and conversion of the guanidinium carbon of arginine in the hydrolysate to carbon dioxide by sequential incubation with arginase and urease. The method is capable of measuring isotopic enrichment as low as 0.001 at.% excess (APE) with a precision of 1.2%. In both subjects studied, the (13C)arginine of VLDL-apoB reached enrichments of 0.2 APE and that of the arginine of LDL-apoB, 0.03 APE. Incorporation of labeled arginine into LDL-apoB was demonstrable at 60-90 min. The new technique is safe and is applicable to the study of the hepatic biosynthesis of a wide range of plasma proteins.
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PMID:Measurement of (C13)arginine incorporation into apolipoprotein B-100 in very low density lipoproteins and low density lipoproteins in normal subjects using (13C)sodium bicarbonate infusion and isotope ratio mass spectrometry. 216 33

We have constructed an opal suppressor system in Escherichia coli to complement an existing amber suppressor system to study the structural basis of tRNA acceptor identity, particularly the role of middle anticodon nucleotide at position 35. The opal suppressor tRNA contains a UCA anticodon and the mRNA of the suppressed protein (which is easily purified and sequenced) contains a UGA nonsense triplet. Opal suppressor tRNAs of two tRNA(Arg) isoacceptor sequences each gave arginine in the suppressed protein, while the corresponding amber suppressors with U35 in their CUA anticodons each gave arginine plus a second amino acid in the suppressed protein. Since C35 but not U35 is present in the anticodon of wild-type tRNA(Arg) molecules, while the first anticodon position contains either C34 or U34, these results establish that C35 contributes to tRNA(Arg) acceptor identity. Initial characterizations of opal suppressor tRNA(Arg) mutants by suppression efficiency measurements suggest that the fourth nucleotide from the 3' end of tRNA(Arg) (A73 or G73 in different isoacceptors) also contributes to tRNA(Arg) acceptor identity. Wild-type and mutant versions of opal and amber tRNA(Lys) suppressors were examined, revealing that U35 and A73 are important determinants of tRNA(Lys) acceptor identity. Several possibilities are discussed for the general significance of having tRNA acceptor identity in the same positions in different tRNA acceptor types, as exemplified by positions 35 and 73 in tRNA(Arg) and tRNA(Lys).
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PMID:Nucleotides that determine Escherichia coli tRNA(Arg) and tRNA(Lys) acceptor identities revealed by analyses of mutant opal and amber suppressor tRNAs. 225 Dec 70

Arginine production was measured in isolated rat nephron segments. Segments were incubated with 0.3 mM aspartate and 0.1 mM L-[ureido-14C]-citrulline in a sealed chamber. Arginase and urease were added to the medium to hydrolyze arginine and to release 14CO2, which was trapped in KOH and counted. Arginine synthesis was found only in the proximal tubule, with decreasing intensity from proximal convoluted (PCT) to proximal straight tubule (PST). Results were as follows (in fmol.min-1.mm tubule length-1): PCT, 122 +/- 15; cortical PST, 71 +/- 6; outer medullary PST, 41 +/- 4; all other segments, less than 6. Arginine synthesis changed almost proportionally with precursor concentration of less than or equal to 0.4 mM. We had shown previously that PST but not PCT was able to hydrolyze arginine into urea and ornithine. In this study arginine was further hydrolyzed in cortical (40%) and medullary (64%) PST but not in PCT. These observations suggest that the arginine formed in PCT contributes to the maintenance of the whole body arginine pool, whereas most of the arginine formed in PST might contribute, by its conversion to urea, to the process of urine concentration.
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PMID:Localization of arginine synthesis along rat nephron. 226 Jun 85

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

Occurrence of a protein controlling urease synthesis (PIUS) at the transcriptional level in the lichen Evernia prunastri has been previously reported (Perez-Urria & Vicente, Physiol Plant 65: 433-438, 1985; id. Endocyt C Res 3: 311-316, 1986). In this work it was found that 0.1 mM cycloheximide seems to inhibit PIUS synthesis when lichen thalli are incubated on PIUS inducer, L-arginine. PIUS has been purified and characterized by PAGE, electrofocusing and amino acid analysis. It is a glycoprotein containing a homopolymer of fructose bound to the protein. PIUS has been located in whole thallus and lichenized mycobiont but remains undetectable in cultured fungi. PIUS is only detected in photobiont cells when they are axenically cultured on arginine. Thus, it is postulated that PIUS could be synthesized by lichenized photobionts from which it moves to mycobionts where it inhibits the production of fungal urease.
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PMID:Algal partner regulates fungal urease in the lichen Evernia prunastri by producing a protein which inhibits urease synthesis. 249 82

Urea production from arginine was studied in vitro in the kidney of normal rats in tubule suspensions of the four different renal zones (cortex, outer and inner stripe of outer medulla, and inner medulla), and in individual microdissected nephron segments. Tissue was incubated with L-[guanido-14C]-arginine to measure cellular arginase activity. Addition of urease to the incubate freed 14CO2 from the 14C-urea formed by arginase and released from the cells. CO2 was trapped in KOH and counted. These experiments revealed that significant amounts of urea are produced in the outer stripe and in the inner medulla. This intrarenal urea generation takes place mainly in the proximal straight tubule and in the collecting duct, with increasing activity in these two structures from superficial to deep regions of the kidney. Urea is known to play a critical role in the urinary concentrating process. The fact that some urea can be produced in the mammalian kidney, and that the two structures showing this capacity are straight portions of the renal tubular system descending along the corticopapillary axis suggest that this urea production might play a role in the formation and/or maintenance of the medullary urea concentration gradient.
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PMID:Production of urea from arginine in pars recta and collecting duct of the rat kidney. 251 52

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

A total of 50 different strains from clinical specimens and/or from experimental surgery were typified. The Staphylococcus genus was subdivided according to minimal test results for Staphylococcus genus differentiation into 3 groups: A. the coagulase-positive/novobiocin-susceptible species; B. the coagulase-negative/novobiocin-resistant species and C. the coagulase-negative/novobiocin-susceptible species. Species belonging to the different groups were differentiated by means of minimal biochemical tests readily available to all clinical bacteriology laboratories. To evaluate the predictive value of the procedure employed, the following strains were used as unknown: S. capitis, S. simulans, S. hominis, S. warneci, S. intermedius, S hyicus subsp. hycus, S hyicus subsp. chromogenes and S. haemolyticus. Results indicated that, for the coagulase-positive/novobiocin-susceptible group, the production of pigment and acetoin plus beta-galactosidase were sufficient for interspecies differentiation. For the coagulase-negative/novobiocin-resistant group, urease and phosphatase activity plus production of acid from xylose proved to be sufficient. The coagulase-negative/novobiocin-susceptible group required the greatest number of tests, due to phenotypical variability of species, including: reduction of nitrates; production of acetoin; use of arginine and the production of acid from maltose and/or trehalose. Preliminary findings justify routine application of these minimal tests for Staphylococcus genus differentiation.
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PMID:[Minimal biochemical tests for interspecies identification in the Staphylococcus genus]. 307 5

The detrimental effects of excessive Ni on plant growth have been well known for many years. More recent evidence indicates that Ni is required in small amounts for normal plant growth and development. Ni is an essential component of urease in plants and microorganisms. A deficiency of Ni in plants is reported to result in necrotic lesions in leaves in response to toxic accumulations of urea. Urease plays an essential role in mobilization of nitrogenous compounds in plants, a process that is especially important during seed germination and fruit formation when protein reserves are degraded into amino acids. Arginine, an abundant amino acid in plants, when degraded produces urea as a product and urease is needed for urea utilization. Theories of urea formation during allantoin degradation in Glycine max have been recently refuted. In G. max ureides apparently are metabolized via an amidohydrolase reaction with subsequent degradation of ureidoglycine, yielding glyoxylate, NH+4 and CO2. No evidence is available for the formation of urea in this pathway. Nitrogen-fixing symbionts, such as Rhizobium and Bradyrhizobium, contain two known Ni enzymes: urease and hydrogenase. Optimum growth of nodulated legumes and actinorhizal plants may depend on an adequate supply of Ni to meet the requirements of the Ni-requiring enzymes in host plants and endophytes. The seeds of severely Ni-deficient Hordeum are completely inviable, thus providing conclusive evidence for the essentiality of Ni for this species. The evidence indicates that Ni must be added to the list of micronutrient elements generally required by plants.
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PMID:Nickel as a micronutrient element for plants. 307 27

Relative deficiencies of ornithine or arginine occur in the presence of excessive ammonia, excessive lysine, growth, pregnancy, trauma, or protein deficiency and malnutrition. Ammonia excess may occur in the presence of a normal liver when amino acid mixtures lacking ornithine, arginine, or citrulline are infused; when specific amino acids such as glycine are injected; when ammonium salts, urea, or urease are injected; or when the gastrointestinal tract contains an excess of protein, urea, or NH4+, as occurs after a gastrointestinal hemorrhage. In these states, ornithine is often rate-limiting for urea cycle function. Ornithine is also rate-limiting when ammonia excess occurs in the presence of hepatic failure. In three of the inherited urea cycle disorders, ornithine insufficiency and ammonia excess also occur. These disorders are citrullinemia, argininosuccinic aciduria, and argininemia. In the presence of excessive lysine the availability of arginine is reduced and the formation of ornithine is decreased in the liver; urea synthesis is reduced, but orotic acid synthesis is increased, and orotic aciduria results as carbamyl phosphate is directed toward the pyrimidine pathway. Hereditary lysinuric protein intolerance results in ornithine depletion, hyperammonemia, and orotic acid uria. Optimal growth in several species of animals requires 0.4-1.0% arginine in the diet. Diets deficient in arginine are associated with poor wound healing as well as stunted growth. The measurement of orotic acid excretion has been a convenient indicator of insufficiency of ornithine or arginine during growth or pregnancy in animals and should prove useful in assessing the requirement for arginine after trauma. Normal human pregnancy is associated with low-grade orotic aciduria. Protein deficiency and malnutrition increase the vulnerability of the animal or child to ammonia toxicity. This is presumably due to insufficient ornithine for normal urea cycle responsiveness.
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PMID:Conditional deficiencies of ornithine or arginine. 308 83


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