Vanadate-stimulated NADH oxidation by xanthine oxidase: An intrinsic property

Khandke, Lakshmi and Gullapalli, Sharada and Patole, Milind S and Ramasarma, T (1986) Vanadate-stimulated NADH oxidation by xanthine oxidase: An intrinsic property. In: Archives of Biochemistry and Biophysics, 244 (2). pp. 742-749.

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Abstract

Vanadate-dependent oxidation of NADH by xanthine oxidase does not require the presence of xanthine and therefore is not due to cooxidation. Addition of NADH or xanthine had no effect on the oxidation of the other substrate. Oxidation of NADH was high at acid pH and oxidation of xanthine was high at alkaline pH. The specific activity was relatively very high with NADH. Concentration-dependent oxidation of NADH was obtained in the presence of the polymeric form of vanadate, but not orthovanadate or metavanadate. Both NADH and NADPH were oxidized, as in the nonenzymatic system. Oxidation of NADH, but not xanthine, was inhibited by KCN, ascorbate, MnCl2, cytochrome c, mannitol, Tris, epinephrine, norepinephrine, and triiodothyronine. Oxidation of NADH was accompanied by uptake of oxygen and generation of H2O2 with a stoichiometry of 1:1:1 for NADH:O2:H2O2. A 240-nm-absorbing species was formed during the reaction which was different from H2O2 or superoxide. A mechanism of NADH oxidation is suggested wherein VV and O2 receive one electron each successively from NADH followed by VIV giving the second electron to superoxide and reducing it to H2O2.

Item Type:	Journal Article
Publication:	Archives of Biochemistry and Biophysics
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	22 Jan 2010 06:40
Last Modified:	19 Sep 2010 05:43
URI:	http://eprints.iisc.ac.in/id/eprint/22789

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