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)

TrzF, the allophanate hydrolase from Enterobacter cloacae strain 99, was cloned, overexpressed in the presence of a chaperone protein, and purified to homogeneity. Native TrzF had a subunit molecular weight of 65,401 and a subunit stoichiometry of alpha(2) and did not contain significant levels of metals. TrzF showed time-dependent inhibition by phenyl phosphorodiamidate and is a member of the amidase signature protein family. TrzF was highly active in the hydrolysis of allophanate but was not active with urea, despite having been previously considered a urea amidolyase. TrzF showed lower activity with malonamate, malonamide, and biuret. The allophanate hydrolase from Pseudomonas sp. strain ADP, AtzF, was also shown to hydrolyze biuret slowly. Since biuret and allophanate are consecutive metabolites in cyanuric acid metabolism, the low level of biuret hydrolase activity can have physiological significance. A recombinant Escherichia coli strain containing atzD, encoding cyanuric acid hydrolase that produces biuret, and atzF grew slowly on cyanuric acid as a source of nitrogen. The amount of growth produced was consistent with the liberation of 3 mol of ammonia from cyanuric acid. In vitro, TrzF was shown to hydrolyze biuret to liberate 3 mol of ammonia. The biuret hydrolyzing activity of TrzF might also be physiologically relevant in native strains. E. cloacae strain 99 grows on cyanuric acid with a significant accumulation of biuret.
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PMID:Purification and characterization of TrzF: biuret hydrolysis by allophanate hydrolase supports growth. 1659 48

Urea amidolyase (UAL) is a multifunctional biotin-dependent enzyme that contributes to both bacterial and fungal pathogenicity by catalyzing the ATP-dependent cleavage of urea into ammonia and CO2 . UAL is comprised of two enzymatic components: urea carboxylase (UC) and allophanate hydrolase (AH). These enzyme activities are encoded on separate but proximally related genes in prokaryotes while, in most fungi, they are encoded by a single gene that produces a fusion enzyme on a single polypeptide chain. It is unclear whether the UC and AH activities are connected through substrate channeling or other forms of direct communication. Here, we use multiple biochemical approaches to demonstrate that there is no substrate channeling or interdomain/intersubunit communication between UC and AH. Neither stable nor transient interactions can be detected between prokaryotic UC and AH and the catalytic efficiencies of UC and AH are independent of one another. Furthermore, an artificial fusion of UC and AH does not significantly alter the AH enzyme activity or catalytic efficiency. These results support the surprising functional independence of AH from UC in both the prokaryotic and fungal UAL enzymes and serve as an important reminder that the evolution of multifunctional enzymes through gene fusion events does not always correlate with enhanced catalytic function.
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PMID:The urea carboxylase and allophanate hydrolase activities of urea amidolyase are functionally independent. 2745 2

This study aimed to identify specific microorganisms related to the formation of precursors of EC (ethyl carbamate) in the solid-state fermentation of Chinese Moutai-flavor liquor. The EC content was significantly correlated with the urea content during the fermentation process (R2 = 0.772, P < 0.01). Differences in urea production and degradation were found at both species and functional gene levels by metatranscriptomic sequencing and culture-dependent analysis. Lactobacillus spp. could competitively degrade arginine through the arginine deiminase pathway with yeasts, and most Lactobacillus species were capable of degrading urea. Some dominant nonconventional yeasts, such as Pichia, Schizosaccharomyces, and Zygosaccharomyces species, were shown to produce low amounts of urea relative to Saccharomyces cerevisiae. Moreover, unusual urea degradation pathways (urea carboxylase, allophanate hydrolase, and ATP-independent urease) were identified. Our results indicate that EC precursor levels in the solid-state fermentation can be controlled using lactic acid bacteria and nonconventional yeasts.
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PMID:Ethyl Carbamate Formation Regulated by Lactic Acid Bacteria and Nonconventional Yeasts in Solid-State Fermentation of Chinese Moutai-Flavor Liquor. 2923 52

Urea is the degradation product of a wide range of nitrogen containing bio-molecules. Urea amidolyase (UA) catalyzes the conversion of urea to ammonium, the essential first step in utilizing urea as a nitrogen source. It is widely distributed in fungi, bacteria and other microorganisms, and plays an important role in nitrogen recycling in the biosphere. UA is composed of urea carboxylase (UC) and allophanate hydrolase (AH) domains, which catalyze sequential reactions. In some organisms UC and AH are encoded by separated genes. We present here structure of the Kluyveromyces lactis UA (KlUA). The structure revealed that KlUA forms a compact homo-dimer with a molecular weight of 400 kDa. Structure inspired biochemical experiments revealed the mechanism of its reaction intermediate translocation, and that the KlUA holo-enzyme formation is essential for its optimal activity. Interestingly, previous studies and ours suggest that UC and AH encoded by separated genes probably do not form a KlUA-like complex, consequently they might not catalyze the urea to ammonium conversion as efficiently.
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PMID:Structure and function of urea amidolyase. 2926 42

Cyanobacteria are widely-diverse prokaryotes that colonize our planet. They use solar energy to assimilate huge amounts of atmospheric CO2 and produce a large part of the biomass and oxygen that sustain most life forms. Cyanobacteria are therefore increasingly studied for basic research objectives, as well as for the photosynthetic production of chemicals with industrial interests. One potential approach to reduce the cost of future bioproduction processes is to couple them with wastewater treatment, often polluted with urea, which in any case is cheaper than nitrate. As of yet, however, research has mostly focused on a very small number of model cyanobacteria growing on nitrate. Thus, the genetic inventory of the cyanobacterial phylum is still insufficiently employed to meaningfully select the right host for the right purpose. This review reports what is known about urea transport and catabolism in cyanobacteria, and what can be inferred from the comparative analysis of the publicly available genome sequence of the 308 cyanobacteria. We found that most cyanobacteria mostly harbor the genes encoding the urea catabolytic enzymes urease (ureABCDEFG), but not systematically, together with the urea transport (urtABCDE). These findings are consistent with the capacity of the few tested cyanobacteria that grow on urea as the sole nitrogen source. They also indicate that urease is important for the detoxification of internally generated urea (re-cycling its carbon and nitrogen). In contrast, several cyanobacteria have urtABCDE but not ureABCDEFG, suggesting that urtABCDE could operate in the transport of not only urea but also of other nutrients. Only four cyanobacteria appeared to have the genes encoding the urea carboxylase (uc) and allophanate hydrolase (ah) enzymes that sequentially catabolize urea. Three of these cyanobacteria belongs to the genera Gloeobacter and Gloeomargarita that have likely diverged early from other cyanobacteria, suggesting that the urea carboxylase and allophanate hydrolase enzymes appeared in cyanobacteria before urease.
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PMID:Genomics of Urea Transport and Catabolism in Cyanobacteria: Biotechnological Implications. 3155 86

Free guanidine is increasingly recognized as a relevant molecule in biological systems. Recently, it was reported that urea carboxylase acts preferentially on guanidine, and consequently, it was considered to participate directly in guanidine biodegradation. Urea carboxylase combines with allophanate hydrolase to comprise the activity of urea amidolyase, an enzyme predominantly found in bacteria and fungi that catalyzes the carboxylation and subsequent hydrolysis of urea to ammonia and carbon dioxide. Here, we demonstrate that urea carboxylase and allophanate hydrolase from Pseudomonas syringae are insufficient to catalyze the decomposition of guanidine. Rather, guanidine is decomposed to ammonia through the combined activities of urea carboxylase, allophanate hydrolase, and two additional proteins of the DUF1989 protein family, expansively annotated as urea carboxylase-associated family proteins. These proteins comprise the subunits of a heterodimeric carboxyguanidine deiminase (CgdAB), which hydrolyzes carboxyguanidine to N-carboxyurea (allophanate). The genes encoding CgdAB colocalize with genes encoding urea carboxylase and allophanate hydrolase. However, 25% of urea carboxylase genes, including all fungal urea amidolyases, do not colocalize with cgdAB. This subset of urea carboxylases correlates with a notable Asp to Asn mutation in the carboxyltransferase active site. Consistent with this observation, we demonstrate that fungal urea amidolyase retains a strong substrate preference for urea. The combined activities of urea carboxylase, carboxyguanidine deiminase and allophanate hydrolase represent a newly recognized pathway for the biodegradation of guanidine. These findings reinforce the relevance of guanidine as a biological metabolite and reveal a broadly distributed group of enzymes that act on guanidine in bacteria.
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PMID:Solving the Conundrum: Widespread Proteins Annotated for Urea Metabolism in Bacteria Are Carboxyguanidine Deiminases Mediating Nitrogen Assimilation from Guanidine. 3278 13


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