Kleczkowski L A, Randall D D, Edwards G E
Department of Biochemistry, University of Missouri, Columbia 65211.
Biochem J. 1991 May 15;276 ( Pt 1)(Pt 1):125-7. doi: 10.1042/bj2760125.
Purified spinach (Spinacia oleracea) NADPH-preferring hydroxypyruvate reductase (HPR-2) was potently and selectively inhibited by oxalate, an end product of metabolism in plants. Both hydroxypyruvate- and glyoxylate-dependent rates of the HPR-2 enzyme were affected. Oxalate acted as an uncompetitive inhibitor of the enzyme, with Ki values of 7 and 36 microM for the NADPH/hydroxypyruvate and NADPH/glyoxylate pairs of reactants respectively. Oxalate, at millimolar levels, caused less than 10% inhibition of purified spinach NADH-preferring HPR (HPR-1) and had no effect on purified spinach NADPH-preferring glyoxylate-specific reductase (GR-1). The inhibition of spinach HPR-2 by oxalate is by far the strongest for any known inhibitor of leaf HPR and GR activities. In photosynthetic tissues, oxalate could potentially act as a primary regulator of extraperoxisomal metabolism of hydroxypyruvate and glyoxylate.
纯化的菠菜（Spinacia oleracea）中偏好NADPH的羟基丙酮酸还原酶（HPR-2）受到草酸盐的强烈且选择性抑制，草酸盐是植物代谢的终产物。HPR-2酶的羟基丙酮酸依赖性和乙醛酸依赖性反应速率均受到影响。草酸盐作为该酶的非竞争性抑制剂，对于NADPH/羟基丙酮酸和NADPH/乙醛酸这两对反应物，其Ki值分别为7和36微摩尔。毫摩尔浓度的草酸盐对纯化的菠菜中偏好NADH的HPR（HPR-1）的抑制作用小于10%，并且对纯化的菠菜中偏好NADPH的乙醛酸特异性还原酶（GR-1）没有影响。就目前已知的对叶片HPR和GR活性的任何抑制剂而言，草酸盐对菠菜HPR-2的抑制作用是最强的。在光合组织中，草酸盐可能潜在地作为羟基丙酮酸和乙醛酸过氧化物酶体代谢外的主要调节剂。
