Identification of the True Product of the Urate Oxidase Reaction

Kahn, Kalju; Serfózó, Péter; Tipton, Peter A.

doi:10.1021/ja970375t

Cited by 145 publications

(155 citation statements)

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“…Tipton and colleagues have provided details of the urate oxidase-catalyzed reaction (5,6) and subsequently identified a gene for HIUHase from soybean (G. max) (7,8). The 560-aa soybean HIUHase does not share any sequence similarity with PucM, but belongs to family 1 of glycosidase (9).…”

Section: Discussionmentioning

confidence: 99%

“…In the ureide pathway, the conversion of uric acid into allantoin was initially thought to involve a single step catalyzed by urate oxidase (E.C. 1.7.3.3; uricase), but recent investigations have revealed that this pathway includes two additional, distinct, chemically labile intermediates: 5-hydroxyisourate (HIU) and 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU) (5,6). It is now generally believed that urate oxidase is responsible only for the conversion of uric acid into HIU, and a second enzyme, HIU hydrolase (HIUHase), catalyzes the hydrolysis of HIU into OHCU (7)(8)(9)(10)(11), which is then converted into allantoin via an enzyme-dependent decarboxylation reaction (Scheme 1) (11).…”

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confidence: 99%

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Structural and functional analysis of PucM, a hydrolase in the ureide pathway and a member of the transthyretin-related protein family

Jung

Lee

Park

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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The ureide pathway, which produces ureides from uric acid, is an essential purine catabolic process for storing and transporting the nitrogen fixed in leguminous plants and some bacteria. PucM from Bacillus subtilis was recently characterized and found to catalyze the second reaction of the pathway, hydrolyzing 5-hydroxyisourate (HIU), a product of uricase in the first step. PucM has 121 amino acid residues and shows high sequence similarity to the functionally unrelated protein transthyretin (TTR), a thyroid hormone-binding protein. Therefore, PucM belongs to the TTRrelated proteins (TRP) family. The crystal structures of PucM at 2.0 Å and its complexes with the substrate analogs 8-azaxanthine and 5,6-diaminouracil reveal that even with their overall structure similarity, homotetrameric PucM and TTR are completely different, both in their electrostatic potential and in the size of the active sites located at the dimeric interface. Nevertheless, the absolutely conserved residues across the TRP family, including His-14, Arg-49, His-105, and the C-terminal Tyr-118 -Arg-119 -Gly-120 -Ser-121, indeed form the active site of PucM. Based on the results of sitedirected mutagenesis of these residues, we propose a possible mechanism for HIU hydrolysis. The PucM structure determined for the TRP family leads to the conclusion that diverse members of the TRP family would function similarly to PucM as HIU hydrolase.5-hydroxyisourate hydrolase ͉ Bacillus subtilis ͉ purine catabolism T he purine de novo biosynthesis is the universal, central metabolic process in all organisms. The pathway begins with glutamine and phosphoribosylpyrophosphate and proceeds through multiple sequential enzymatic steps to the end product inosine monophosphate, which is subsequently used as the precursor for the biosynthesis of other purine nucleotides (1, 2). Some bacteria use the nitrogen in purine bases as an energy source under nitrogen-limited conditions. Therefore, the catabolic pathway degrading purine nucleotides has been proposed to be an essential metabolic process (reviewed in refs. 3 and 4). Uric acid, a major intermediate of purine catabolism, can be excreted or subjected to further degradation, depending on the presence of unique enzyme systems in different organisms. Sequential enzymatic reactions using uric acid as a substrate result in ureides, including allantoin and allantoate (Scheme 1) (1,3,4). This ureide pathway plays a vital role in transporting and storing the nitrogen fixed in leguminous plants in the form of ureides, which have a relatively high N-to-C ratio of 1.0. Moreover, symbiotic N 2 -fixing bacteria actively supply the available nitrogen, which is in turn assimilated into glutamine, a substrate in the first step of purine biosynthesis. In the ureide pathway, the conversion of uric acid into allantoin was initially thought to involve a single step catalyzed by urate oxidase (E.C. 1.7.3.3; uricase), but recent investigations have revealed that this pathway includes two additional, distinct, chemically labile intermedi...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Structural and functional analysis of PucM, a hydrolase in the ureide pathway and a member of the transthyretin-related protein family

Jung

Lee

Park

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…The exact catalytic mechanism is still not fully understood, there is no cofactor nor metallic ion, the optimal pH is basic (between 8.5 and 9), and it is known for a long time that the oxygen atoms in H 2 O 2 derive from those of O 2 [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Functional relevance of the internal hydrophobic cavity of urate oxidase

Colloc’h

Prangé

2014

FEBS Letters

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a b s t r a c tUrate oxidase from Aspergillus flavus is a 135 kDa homo-tetramer which has a hydrophobic cavity buried within each monomer and located close to its active site. Crystallographic studies under moderate gas pressure and high hydrostatic pressure have shown that both gas presence and high pressure would rigidify the cavity leading to an inhibition of the catalytic activity. Analysis of the cavity volume variations and functional modifications suggest that the flexibility of the cavity would be an essential parameter for the active site efficiency. This cavity would act as a connecting vessel to give flexibility to the neighboring active site, and its expansion under pure oxygen pressure reveals that it might serve as a transient reservoir on its pathway to the active site.

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“…1d). Based on these results, and the observation of 5-hydroxyuric acid in the uric acid degradation pathway (22), metabolite II (TM-HIU) was proposed as the true product of TMU monooxygenase reaction. Metabolite II (TM-HIU) was unstable under the reaction condition and spontaneously converted to TMA (possibly via metabolite III), as is the case in the uric acid degradation pathway (8,31,32).…”

Section: Resultsmentioning

confidence: 94%

Delineation of the Caffeine C-8 Oxidation Pathway in Pseudomonas sp. Strain CBB1 via Characterization of a New Trimethyluric Acid Monooxygenase and Genes Involved in Trimethyluric Acid Metabolism

Mohanty

Das

et al. 2012

J Bacteriol

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The molecular basis of the ability of bacteria to live on caffeine via the C-8 oxidation pathway is unknown. The first step of this pathway, caffeine to trimethyluric acid (TMU), has been attributed to poorly characterized caffeine oxidases and a novel quinone-dependent caffeine dehydrogenase. Here, we report the detailed characterization of the second enzyme, a novel NADHdependent trimethyluric acid monooxygenase (TmuM), a flavoprotein that catalyzes the conversion of TMU to 1,3,7-trimethyl-5-hydroxyisourate (TM-HIU). This product spontaneously decomposes to racemic 3,6,8-trimethylallantoin (TMA). TmuM prefers trimethyluric acids and, to a lesser extent, dimethyluric acids as substrates, but it exhibits no activity on uric acid. Homology models of TmuM against uric acid oxidase HpxO (which catalyzes uric acid to 5-hydroxyisourate) reveal a much bigger and hydrophobic cavity to accommodate the larger substrates. Genes involved in the caffeine C-8 oxidation pathway are located in a 25.2-kb genomic DNA fragment of CBB1, including cdhABC (coding for caffeine dehydrogenase) and tmuM (coding for TmuM).

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Identification of the True Product of the Urate Oxidase Reaction

Cited by 145 publications

References 38 publications

Structural and functional analysis of PucM, a hydrolase in the ureide pathway and a member of the transthyretin-related protein family

Structural and functional analysis of PucM, a hydrolase in the ureide pathway and a member of the transthyretin-related protein family

Functional relevance of the internal hydrophobic cavity of urate oxidase

Delineation of the Caffeine C-8 Oxidation Pathway in Pseudomonas sp. Strain CBB1 via Characterization of a New Trimethyluric Acid Monooxygenase and Genes Involved in Trimethyluric Acid Metabolism

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