Details

Autor(en) / Beteiligte

• Khandke, Lakshmi
• Gullapalli, Sharada
• Patole, Milind S.
• Ramasarma, T.

Titel

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

Ist Teil von

• Archives of biochemistry and biophysics, 1986-02, Vol.244 (2), p.742-749

Ort / Verlag

San Diego, CA: Elsevier Inc

Erscheinungsjahr

1986

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• 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, MnCl 2, cytochrome c, mannitol, Tris, epinephrine, norepinephrine, and triiodothyronine. Oxidation of NADH was accompanied by uptake of oxygen and generation of H 2O 2 with a stoichiometry of 1:1:1 for NADH:O 2:H 2O 2. A 240-nm-absorbing species was formed during the reaction which was different from H 2O 2 or superoxide. A mechanism of NADH oxidation is suggested wherein V V and O 2 receive one electron each successively from NADH followed by V IV giving the second electron to superoxide and reducing it to H 2O 2.