Involvement of a single thiol group in the conversion of the NAD+-dependent activity of rat liver xanthine oxidoreductase to the O2-dependent activity

Kamiński, Zbigniew; Jeżewska, Maria

doi:10.1042/bj2070341

Cited by 24 publications

(8 citation statements)

References 19 publications

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“…This enhancement may be due to xanthine dehydrogenase, which is present in liver slices. Xanthine oxidase differs from xanthine dehydrogenase in the presence of a sulphydryl group (32). Conversion of xanthine oxidase from dehydrogenase (0 form) into an oxidase (0 form) occurs upon oxidation or binding of sulphydryl groups by several oxidising agents or ligands (33,34).…”

Section: Resultsmentioning

confidence: 99%

Metabolism of 2-phenylethylamine and phenylacetaldehyde by precision-cut guinea pig fresh liver slices

Panoutsopoulos

Kouretas

Gounaris

et al. 2004

European Journal of Drug Metabolism and Pharmacokinetics

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2-Phenylethylamine is an endogenous constituent of human brain and is implicated in cerebral transmission. It is also found in certain foodstuffs and may cause toxic side-effects in susceptible individuals. Metabolism of 2-phenylethylamine to phenylacetaldehyde is catalyzed by monoamine oxidase and the oxidation of the reactive aldehyde to its acid derivative is catalyzed mainly by aldehyde dehydrogenase and perhaps aldehyde oxidase, with xanthine oxidase having minimal transformation. The present investigation examines the metabolism of 2-phenylethylamine to phenylacetaldehyde in liver slices and compares the relative contribution of aldehyde oxidase, xanthine oxidase and aldehyde dehydrogenase activity in the oxidation of phenylacetaldehyde with precision-cut fresh liver slices in the presence/absence of specific inhibitors of each enzyme. In liver slices, phenylacetaldehyde was rapidly converted to phenylacetic acid. Phenylacetic acid was the main metabolite of 2-phenylethylamine, via the intermediate phenylacetaldehyde. Phenylacetic acid formation was completely inhibited by disulfiram (specific inhibitor of aldehyde dehydrogenase), whereas isovanillin (specific inhibitor of aldehyde oxidase) inhibited acid formation to a lesser extent and allopurinol (specific inhibitor of xanthine oxidase) had little or no effect. Therefore, in liver slices, phenylacetaldehyde is rapidly oxidized by aldehyde dehydrogenase and aldehyde oxidase with little or no contribution from xanthine oxidase.

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Section: Resultsmentioning

confidence: 99%

Metabolism of 2-phenylethylamine and phenylacetaldehyde by precision-cut guinea pig fresh liver slices

Panoutsopoulos

Kouretas

Gounaris

et al. 2004

European Journal of Drug Metabolism and Pharmacokinetics

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“…It is likely that parts of cysteine residues are close enough to readily form disulfide bridges within the enzyme because cysteine disulfide bridges were formed by reaction with 4-PDS rather than single cysteine residues being modified (8,17). Although it has been reported that a single cysteine residue is involved in the conversion (18), the method employed in the report is not appropriate for the determination of the number of residues in chemical modification studies, as discussed by Rakitzis (19).…”

mentioning

confidence: 87%

The Conversion from the Dehydrogenase Type to the Oxidase Type of Rat Liver Xanthine Dehydrogenase by Modification of Cysteine Residues with Fluorodinitrobenzene

Nishino

1997

Journal of Biological Chemistry

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When rat liver xanthine dehydrogenase was incubated with fluorodinitrobenzene (FDNB) at pH 8.5, the total enzyme activity decreased gradually to a limited value of initial activity with modification of two lysine residues in a similar way to the modification of bovine milk xanthine oxidase with FDNB (Nishino, T., Tsushima, K., Hille, R. and Massey, V. (1982) J. Biol. Chem. 257, 7348 -7353). After modification with FDNB, the two peptides containing dinitrophenyl-lysine were isolated from the molybdopterin domain after proteolytic digestion and were identified as Lys 754 and Lys 771by sequencing the peptides. During the modification of these lysine residues, xanthine dehydrogenase was found to be converted to an oxidase form in the early stage of incubation. Incorporation of the 3 H-dinitrophenyl group into enzyme cysteine residues was 0.96 mol per enzyme FAD for 68% conversion to the oxidase form. The modified enzyme was reconverted to the dehydrogenase form by incubation with dithiothreitol with concomitant release of 3 H-dinitrophenyl compounds. After modification with 3 H-FDNB followed by carboxymethylation under denaturating conditions, the enzyme was digested with proteases. Three 3 H-dinitrophenyl-labeled peptides were isolated and sequenced. The modified residues were identified to be Cys 535 , Cys 992 and Cys 1324 . These residues are conserved among the all known mammalian enzymes, but Cys 992 and Cys 1324 are not conserved in the chicken enzyme. Cys 1324 of the rat enzyme was found not to be involved in the conversion from the dehydrogenase to the oxidase by limited proteolysis experiments, but Cys 535 and Cys 992 which seemed to be modified alternatively with FDNB appear to be involved in the conversion. Xanthine oxidase (XO)1 catalyzes the oxidation of xanthine using molecular oxygen as an electron acceptor. The enzyme is a dimer containing one FAD, two 2Fe/2S centers, and one molybdopterin cofactor per M r 150,000 subunit (1, 2). Mammalian XO exists as the NAD-dependent dehydrogenase type (XDH) in freshly prepared samples, i.e. it exhibits low xanthine-O 2 reductase activity but high xanthine-NAD reductase activity even in the presence of O 2 (3, 4). But during extraction or purification procedures, the enzyme can be easily converted to an O 2 -dependent oxidase type (XO), i.e. it exhibits low xanthine-NAD activity but high xanthine-O 2 reductase activity. This conversion occurs reversibly by oxidation of sulfhydryl groups or irreversibly through proteolysis (3-10). As H 2 O 2 and O 2 Ϫ are formed as products when molecular oxygen is used as an electron acceptor, the conversion from XDH to XO has been proposed as the basis of the mechanism of recirculation injury (11).Although the enzyme is easily converted to XO, the enzyme can be purified as the dehydrogenase (XDH) form by rapid purification (6) or in the presence of thiol reagents such as mercaptoethanol or DTT (7, 8), or as an XO form which can be converted to XDH by incubation with thiols (9). The differences in structural, spectroscopic and kin...

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“…this conversion can be reversible, through oxidation of key cysteine residues, or irreversible, by limited proteolysis. *** ,157,236-252 however, the extent and *** it is to be emphasized that mammalian Xo and Xd are two forms of the same protein (same gene product) that arise as the result of posttranslational conformational modifications (oxidation of key cysteine residues or limited proteolysis); 157, [236][237][238][239][240][241][242][243][244][245][246][247][248][249][250][251][252] to designate the two forms, without regard to the oxidizing substrate, it is preferable to use the denomination "xanthine oxidoreductase". the only functional distinction between Xd and Xo lies in the electron acceptor used by each form: while Xd transfers the electrons preferentially to nad + (but it can also reduce dioxygen), Xo fails to react with nad + and uses exclusively dioxygen.…”

Section: The Xanthine Oxidase Familymentioning

confidence: 99%

CHAPTER 1. Molybdenum and Tungsten-Containing Enzymes: An Overview

Maia¹,

Moura²,

Moura³

2016

Molybdenum and Tungsten Enzymes

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Involvement of a single thiol group in the conversion of the NAD+-dependent activity of rat liver xanthine oxidoreductase to the O2-dependent activity

Cited by 24 publications

References 19 publications

Metabolism of 2-phenylethylamine and phenylacetaldehyde by precision-cut guinea pig fresh liver slices

Metabolism of 2-phenylethylamine and phenylacetaldehyde by precision-cut guinea pig fresh liver slices

The Conversion from the Dehydrogenase Type to the Oxidase Type of Rat Liver Xanthine Dehydrogenase by Modification of Cysteine Residues with Fluorodinitrobenzene

CHAPTER 1. Molybdenum and Tungsten-Containing Enzymes: An Overview

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