On the mechanism of rotenone‐insensitive reduction of quinones by mitochondrial NADH:ubiquinone reductase The high affinity binding of NAD+ and NADH to the reduced enzyme form

FEBS Letters

Čénas, Narimantas K.¹  Kulys, Juozas J.¹  Bironaité, Daiva A.¹ 

[1] Institute of Biochemistry, Lithuanian Academy of Sciences, 232021 Vilnius Mokslininku 12, Lithuania, USSR

关键词: NADH:ubiquinone reductase;    Electron acceptor;    Steady-state kinetics;    TN;    turnover number;    TN/K m;    biomolecular rate constant;   

DOI  :  10.1016/0014-5793(91)80682-S

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

NADH acts as an incomplete competitive inhibitor for 5,8-dioxy-1,4-naphtoquinone during its rotenone-insensitive reduction by mitochondrial NADH:ubiquinone reductase. NAD⁺ and ADP-ribose act as incomplete mixed-type inhibitors. K _i of NAD⁺ and NADH towards quinone are about one order less than towards ferricyanide. The bimolecular rate constant of the reduction of the enzyme by NADH in the quinone reductase reaction is about 2 times less than that of ferricyanide reductase reaction. These data indicate that the reduction site of 5,8-dioxy-1,4-naphtoquinone is close to NAD⁺/NADH and ferricyanide binding site. It seems that during the steady-state reduction of ferricyanide and 5,8-dioxy-1,4-naphtoquinone these oxidizers react with NADH:ubiquinone reductase reduced to different extents.

【 授权许可】

Unknown