Biochemistry Department, 322A Chemistry Building, University of Missouri, Columbia, Missouri 65211.
Plant Physiol. 1987 Feb;83(2):306-10. doi: 10.1104/pp.83.2.306.
The pyruvate dehydrogenase complex was isolated, partially purified, and characterized from green pea (Pisum sativum L., cv Little Marvel) leaf mitochondria. The pH optimum for the overall reaction was 7.6. The divalent cation requirement was best satisfied by Mg(2+). Reaction velocity was maximal at 40 degrees C. Pyruvate was a better substrate than 2-oxo-butyrate; other 2-oxo-acids were not substrates. Michaelis constants for substrates were; pyruvate, 57 micromolar; NAD, 122 micromolar; Coenzyme-A, 5 micromolar; Mg(2+), 0.36 millimolar; Mg-thiamine pyrophosphate, 80 nanomolar. The products, NADH and acetyl-Coenzyme-A, were linear competitive inhibitors with respect to NAD and Coenzyme A. Inhibition constants were 18 and 10 micromolar, respectively. Glyoxylate inhibited complex activity only in the absence of thiol reagents. Glyoxylate inhibition was competitive with respect to pyruvate with an inhibition constant of 51 micromolar. Among mitochondrial metabolites examined as potential effectors, only ADP with an inhibition constant of 0.57 millimolar could be of physiological significance.
从绿豌豆（Pisum sativum L.，cv Little Marvel）叶线粒体中分离、部分纯化并鉴定了丙酮酸脱氢酶复合物。整体反应的 pH 最适值为 7.6。二价阳离子的最佳需求是 Mg(2+)。反应速度在 40°C 时达到最大值。丙酮酸是比 2-氧代丁酸更好的底物；其他 2-氧代酸不是底物。底物的米氏常数为：丙酮酸，57 微摩尔；NAD，122 微摩尔；辅酶 A，5 微摩尔；Mg(2+)，0.36 毫摩尔；Mg-硫胺素焦磷酸，80 纳摩尔。产物 NADH 和乙酰辅酶 A 对 NAD 和辅酶 A 呈线性竞争抑制。抑制常数分别为 18 和 10 微摩尔。甘氨酸在线粒体代谢物中仅在不存在硫醇试剂的情况下抑制复合物的活性。甘氨酸抑制是与丙酮酸竞争的，抑制常数为 51 微摩尔。在所检查的线粒体代谢物中，只有作为潜在效应物的 ADP 的抑制常数为 0.57 毫摩尔，可能具有生理意义。
