醋酸棉酚对乳酸脱氢酶同工酶的抑制动力学

Inhibition kinetics of lactate dehydrogenase isoenzymes by gossypol acetic acid.

作者信息

Gupta G S, Kapur S, Kinsky R G

机构信息

Department of Biophysics, Panjab University, Chandigarh, India.

出版信息

Biochem Int. 1988 Jul;17(1):25-34.

PMID:3190716

Abstract

The effect of gossypol acetic acid, a potent male sterilent was studied on LDH from goat liver (LDH-A4), heart (LDH-B4) and testis (LDH-C4) in vitro. All the preparations of LDH were inhibited by gossypol when the reaction was carried out in pyruvate-lactate (direct) or lactate to pyruvate (reverse) directions. The IC50 of gossypol for the pyruvate oxidation by LDH isozymes varied between 16 and 42 microM in presence of 0.27 mM pyruvate and 0.15 mM NADH at 25 degrees C and pH 7.4 whereas for the lactate oxidation, IC50 was 125 microM in a system containing 3.3 mM lactic acid and 1.8 mM NAD at 25 degrees C and pH 9.0. Reciprocal plots due to Lineweaver-Burk showed that these isozymes are inhibited in a non-competitive manner with respect to pyruvate and lactate, and in a competitive fashion when NAD and NADH were varied as substrates. Ki values of LDH-A4, -B4 and -C4 isozymes in presence of gossypol were 20, 34 and 29 microM against pyruvate; 33, 43 and 45 microM against NADH; 85, 85 and 125 microM against lactate and 94, 108 and 83 microM against NAD respectively.

摘要

研究了强效雄性绝育剂醋酸棉酚对山羊肝脏（LDH-A4）、心脏（LDH-B4）和睾丸（LDH-C4）中乳酸脱氢酶（LDH）的体外作用。当反应在丙酮酸-乳酸（正向）或乳酸-丙酮酸（反向）方向进行时，所有LDH制剂均受到醋酸棉酚的抑制。在25℃和pH 7.4条件下，存在0.27 mM丙酮酸和0.15 mM NADH时，醋酸棉酚对LDH同工酶氧化丙酮酸的IC50在16至42 microM之间；而在25℃和pH 9.0条件下，在含有3.3 mM乳酸和1.8 mM NAD的体系中，对乳酸氧化的IC50为125 microM。Lineweaver-Burk双倒数作图表明，这些同工酶对丙酮酸和乳酸的抑制方式为非竞争性，而当NAD和NADH作为底物变化时，抑制方式为竞争性。在存在醋酸棉酚的情况下，LDH-A4、-B4和-C4同工酶对丙酮酸的Ki值分别为20、34和29 microM；对NADH的Ki值分别为33、43和45 microM；对乳酸的Ki值分别为85、85和125 microM；对NAD的Ki值分别为94、108和83 microM。