Tracing and identification of uricase. Reaction intermediates.

Modrić, Nevenka; Derome, Andrew E.; Ashcroft, S. J. H.; Poje, M.

doi:10.1016/s0040-4039(00)61021-3

Cited by 36 publications

(27 citation statements)

References 16 publications

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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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Section: Introductionmentioning

confidence: 99%

Functional relevance of the internal hydrophobic cavity of urate oxidase

Colloc’h

Prangé

2014

FEBS Letters

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“…It is commonly considered that the role of urate oxidase in this pathway is the conversion of urate to allantoin (3). However, it has recently been demonstrated that allantoin is not the true product of the urate oxidase reaction (4,5). Urate oxidase catalyzes the conversion of urate to 5-hydroxyisourate, which decomposes cleanly to allantoin under most in vitro conditions.…”

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confidence: 99%

Identification and Purification of Hydroxyisourate Hydrolase, a Novel Ureide-metabolizing Enzyme

Sarma

Serfózó

Kahn

et al. 1999

Journal of Biological Chemistry

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We report the identification and purification of a novel enzyme from soybean root nodules that catalyzes the hydrolysis of 5-hydroxyisourate, which is the true product of the urate oxidase reaction. The product of this reaction is 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline, and the new enzyme is designated 5-hydroxyisourate hydrolase. The enzyme was purified from crude extracts of soybean root nodules ϳ100-fold to apparent homogeneity with a final specific activity of 10 mol/ min/mg. The enzyme exhibited a native molecular mass of ϳ68 kDa by gel filtration chromatography and migrated as a single band on SDS-polyacrylamide gel electrophoresis with a subunit molecular mass of 68 ؎ 2 kDa. The purified enzyme obeyed normal Michaelis-Menten kinetics, and the K m for 5-hydroxyisourate was determined to be 15 M. The amino-terminal end of the purified protein was sequenced, and the resulting sequence was not found in any available data bases, confirming the novelty of the protein. These data suggest the existence of a hitherto unrecognized enzymatic pathway for the formation of allantoin.Nitrogen is a key component of plant metabolism, and its availability often limits the growth of important crop plants. Leguminous plants are able to acquire their nitrogen through association with bacterial symbionts in the root nodules, which fix atmospheric nitrogen to form NH 4 ϩ through the action of nitrogenase. The fixed nitrogen is then transported from the bacteria into the host cell cytoplasm, where it is assimilated into organic form and used for the synthesis of nucleic acids, amino acids, and secondary products.The ureides are the major form of nitrogen transport molecules in tropical legumes such as soybean. In nodulated soybean ureides constitute 70 -80% of the organic nitrogen in the xylem sap (1). The ureides are efficient nitrogen transport species; the ratio of C to N in allantoin and allantoate is 1:1, so minimal carbon is diverted from other metabolic functions in support of nitrogen transport. The conversion of inorganic nitrogen into organic forms is an energetically expensive process, however. It has been estimated that 68 ATPs are required for the synthesis of allantoin if the cost of N 2 fixation is included (2). Thus, one would expect mechanisms for the efficient utilization of fixed nitrogen to have arisen.Purine oxidation is the major route for ureide biogenesis, and the so-called ureide pathway is constituted by the enzymes that carry out the conversion of IMP to allantoin and allantoate. It is commonly considered that the role of urate oxidase in this pathway is the conversion of urate to allantoin (3). However, it has recently been demonstrated that allantoin is not the true product of the urate oxidase reaction (4, 5). Urate oxidase catalyzes the conversion of urate to 5-hydroxyisourate, which decomposes cleanly to allantoin under most in vitro conditions.The half-life of HIU 1 at neutral pH is on the order of 30 min in vitro (6). Because the flux through the ureide pathway is critical for nitrogen fi...

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“…The free energy of single-electron transfer in aqueous solution is given by Eq. [1], where IP refers to the adiabatic ionization potential of the electron donor and EA is the adiabatic electron affinity of the acceptor. Equation [2] is used to calculate the difference in solvation energies of superoxide and urate anion from the corresponding aqueous pK a values and gas-phase basicities (GB) of anions.…”

Section: Figmentioning

confidence: 99%

“…Urate oxidase functions in the purine degradation pathway and catalyzes the reaction between urate monoanion and dioxygen to give 5-hydroxyisourate and hydrogen peroxide (Scheme 1) (1,2). Oxidation of urate to more soluble compounds is required for the excretion of excess nitrogen in most mammals (3,4); the same reaction plays an important role in the transport of de novo fixed nitrogen throughout the plant in soybean and some other tropical legumes (5).…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Intermediates in the Urate Oxidase Reaction

Kahn

1999

Bioorganic Chemistry

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Tracing and identification of uricase. Reaction intermediates.

Cited by 36 publications

References 16 publications

Functional relevance of the internal hydrophobic cavity of urate oxidase

Functional relevance of the internal hydrophobic cavity of urate oxidase

Identification and Purification of Hydroxyisourate Hydrolase, a Novel Ureide-metabolizing Enzyme

Theoretical Study of Intermediates in the Urate Oxidase Reaction

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