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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 urea-hydrolyzing activity of a T-strain mycoplasma was studied in experiments using whole cells and cell-free enzyme preparations by measuring the release of 14CO2 from [14C]urea. Under the conditions used, the urea concentration optimum is approximately 5.6 X 10(-3) M urea. The activity is soluble and not membrane bound. It is stable at -70 C for several weeks but is more labile at higher temperatures. The pH optimum is between 5.0 and 6.0. The effect of several inhibitors on the activity was tested and revealed similarities, as well as differences, between T-strain mycoplasma urease activity and the urease activity of other organisms and plants.
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PMID:Urea-hydrolyzing activity of a T-strain mycoplasma: Ureaplasma urealyticum. 0 81

Ureaplasma urealyticum cells were lysed by osmotic shock or by digitonin. The membrane fraction contained four to ten times as much protein as the cytoplasmic fraction. These values are in large excess of those reported for classical mycoplasmas, suggesting that the Ureaplasma membrane fraction was heavily contaminated with proteins derived from the growth medium. The U. urealyticum urease activity was localized in the cytoplasmic fraction, whereas the adenosine triphosphatase activity was localized in the membrane fraction. Significant urease activity could be detected also in nonviable cells. Urea, at concentrations above 0.25 M, was mycoplasmastatic to Acholeplasma laidlawii, Mycoplasma hominis, and U. urealyticum, so that the Ureaplasma urease did not afford preferential protection against urea toxicity. The intracellular localization of the urease would be expected to release ammonia from urea in the cytoplasm. The ammonia will take up protons to become ammonium ions. It can be hypothesized that the intracellular NH4+ plays a role in proton elimination or acid-base balance, which might be coupled to an energy producing ion gradient and/or transport mechanisms.
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PMID:Localization of enzymes in Ureaplasma urealyticum (T-strain mycoplasma). 1 80

The localization of some enzymic activities in cell fractions of Ureaplasma urealyticum was studied. A quantitative evaluation of the effectiveness of several cell lysis procedures was obtained by using labeled membranes and sucrose density gradient centrifugation. Ultrasonic treatment was found to be the most effective procedure for lysing the cells, whereas digitonin and osmotic shock caused the lysis of only 70 and 50% of the cells, respectively. The localization of selected enzymes in Ureaplasma cells resembled that found in other Mycoplasma species. Adenosine triphosphatase, ribonuclease, deoxyribonuclease, and p-nitrophenylphosphatase activities were located exclusively in the membrane fraction, whereas urease and L-histidine ammonia-lyase were located in the cytoplasm.
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PMID:Cell fractions and enzymatic activities of Ureaplasma urealyticum. 21 22

Urethral swabs from 75 males with urethritis were extracted into tryptose phosphate broth and then equal aliquots were dispensed into vials containing sucrose phosphate buffer (2SP) and urease color test medium (U-9). No antibiotics were present in the media. After transport to the laboratory, the recovery of Chlamydia trachomatis and Ureaplasma urealyticum was evaluated after inoculation into McCoy's cell cultures and agar medium, respectively. C. trachomatis was recovered from significantly more patients (17 versus 12, P = 0.03) with higher inclusion counts (P less than 0.01) in specimens transported in 2SP as compared with those in U-9 medium. No significant differences between the isolation rate of U. urealyticum and that of Mycoplasma hominis were found with the two media. The rate of inactivation of C. trachomatis and U. realyticum at 4 C was examined by means of reference strains. The inactivation of C. trachomatis was similar in both 2SP and U-9 media, but the number of inclusions was consistently greater in the 2SP medium. In contrast, the number of colony-forming units of U. urealyticum actually increased over a 24-hour period in both media. We conclude that 2SP is the best medium for the combined recovery of C. trachomatis and genital Mycoplasma. The use of one transport medium and hence a single swab culture has the obvious advantages of saving time and expense for both physician and laboratory, and for the patient it will eliminate the possible discomfort of having multiple cultures taken.
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PMID:Recovery of Chlamydia and Genital Mycoplasma transported in sucrose phosphate buffer and urease color test medium. 31 81

The possibility to keep some biochemical reactions of the parent strains (urease-positive, glucose fermentation, phenylalanine-deaminase-positive, H2S but not indol production) was demonstrated in 5 L-forms, obtained from as many strains of Pr. mirabilis and in 1 L-form, isolated from a vaginal secretion and identified as belonging to the same species. The indirect hemagglutination technique, made by the sonicated antigen in 3 of the 6 L-forms with Proteus OXK antiserum, resulted positive in titers varying from 1:128 to 1:1024. Crossed tests made with antisera for different bacterial species (e. coli, Shigella, klebsiella, ecc.) and of Mycoplasma (M. hominis, M. orale, M. salivarium, M. fermentans, M. arthritidis) put in evidence aspecific reactions only in 1.3% of the bacterial antisera. On the contrary, all 5 antisera for Mycoplasma were able to agglutinate the sensitized erythrocytes at titers quite analogous to that of the homologous antiserum. The sensitivities to various antibiotics of the 6 L-forms and the parent strains has been determined. All of L-forms were more resistent to the tetracycline than L-forms of other bacterial species. On the basis of te results got by biochemical and serological tests, we confirm the necessity to make use of both the groups of tests, in order to identify the L-forms of recent isolation.
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PMID:[Researches on some biochemical and serological properties and on the sensitivity to antibiotics of L-forms of "Proteus" (author's transl)]. 40 87

Bromothymol blue (B) broth for the cultivation, detection, and identification of Ureaplasma urealyticum is described. In this medium, strains Cook and 960 had shorter generation times (60 min or less) and reached higher populations (over 10(8)) than have yet been reported for this species. Furthermore, the indicator changes color before the end of logarithmic growth, and the cultures retain viability for at least 1 day thereafter, greatly simplifying the handling of the organism. When the populations in cultures of these two strains and seven new isolates were determined, growth was detected earlier and proceeded to higher final titers in B broth than in urease test color medium (U-9 broth). The inclusion of antibiotics in B broth for use in clinical laboratories (B/NL broth) made the medium selective, specific, and more sensitive for the isolation of U. urealyticum. Comparison of B/NL broth with genital mycoplasma (GM) agar and U-9 broth for the primary isolation of U. urealyticum was made with 183 urethral swabs. All 70 isolates were detected on B/NL broth, but only 66 and 63 isolates were detected on GM agar and in U-9 broth, respectively. Moreover, the cultures in B/NL broth were pure and at titers that generally showed good correlation with colony counts on GM agar.
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PMID:Bromothymol blue broth: improved medium for detection of Ureaplasma urealyticum (T-strain mycoplasma). 63 44

Mycoplasms were isolated from 35 (16%) of 215 specimens collected from 20 crab-eating monkeys (Macaca irus), 9 green monkeys (Cercopithecus aethiops) and from 9 common squirrel monkeys (Saimiri sciurea). All these animals had been imported from South-East Asia, Africa and South America being apparently healthy. A total of 38 large and 20 small colony-mycoplasma strains were isolated from the nasal and oral cavity, urethra, vagina and rectal feces. The large colony-mycoplasmas could be differentiated into 5 groups on the basis of their biological and serological characteristics. Six and 7 of them were identified as M. orale 2 and M. salivarium, respectively. Twenty strains were clearly distinguished not only from M. orale 2 and M. salivarium, but also from such arginase positive species as M. orale 1, M. fermentans, M. hominis, M. arthritidis, M. maculosum and M. gateae. These were divided into 2 groups, comprising 9 and 11 strains, respectively, by growth inhibition as well as various biological tests. The remaining 5 strains were not identified serologically. The small colony-mycoplasmas were found to be urease-positive and appeared to be T-mycoplasmas, while not examined serologically.
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PMID:[Characterization of Mycoplasms isolated from imported nonhuman primates (author's transl)]. 81 74

Struvite bladder calculi were induced in rats with an intrarenal injection of urease-producing human T mycoplasma strain T960. Acetohydroxamic acid was effective in inhibiting calculous formation. Methylene blue, tetracycline, orthophosphate, diphosphonate, and hydrochlorothiazide had no inhibitory effect.
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PMID:Medical therapy of experimental infection stones. 91 29

A differential agar medium for the identification of Ureaplasma urealyticum in primary cultures of clinical specimens is described. The differential medium (no. A7) is specific for the identification of U. urealyticum and other members of the genus Ureaplasma. Large-colony, classical Mycoplasma and Acholeplasma species and Proteus L colonies are unreactive on this differential medium. The medium incorporates the biochemical principle of the direct spot test for urease in colonies of Ureaplasma and contains added urea and a sensitive indicator of ammonia, manganous sulfate. Ureaplasma colonies on this medium are identified as dark golden-brown or rich deep-brown colonies, in sharp contrast to the light background of the medium, when viewed by direct transmitted illumination under the low power of the microscope.
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PMID:Differential agar medium (A7) for identification of Ureaplasma urealyticum (human T mycoplasmas) in primary cultures of clinical material. 95 Mar 79

The middle base (U35) of the anticodon of tRNA(Gln) is a major element ensuring the accuracy of aminoacylation by Escherichia coli glutaminyl-tRNA synthetase (GlnRS). An opal suppressor of tRNA(Gln) (su+2UGA) containing C35 (anticodon UCA) was isolated by genetic selection and mutagenesis. Suppression of a UGA mutation in the E. coli fol gene followed by N-terminal sequence analysis of purified dihydrofolate reductase showed that this tRNA was an efficient suppressor that inserted predominantly tryptophan. Mutations of the 3-70 base pair (U70 and A3U70) were made. These mutants of su+2UGA are less efficient suppressors and inserted predominantly tryptophan in vivo; alanine insertion was not observed. Mutations of the discriminator nucleotide (A73, U73, C73) result in very weak opal suppressors. Aminoacylation in vitro by E. coli TrpRS of tRNA(Gln) transcripts mutated in the anticodon demonstrate that TrpRS recognizes all three nucleotides of the anticodon. The results show the interchangeability of the glutamine and tryptophan identities by base substitutions in their respective tRNAs. The amber suppressor (anticodon CUA) tRNA(Trp) was known previously to insert predominantly glutamine. We show that the opal suppressor (anticodon UCA) tRNA(Gln) inserts mainly tryptophan. Discrimination by these synthetases for tRNA includes position 35, with recognition of C35 by TrpRS and U35 by GlnRS. As the use of the UGA codon as tryptophan in mycoplasma and in yeast mitochondria is conserved, recognition of the UCA anticodon by TrpRS may also be maintained in evolution.
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PMID:Switching tRNA(Gln) identity from glutamine to tryptophan. 156 39


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