Department of Medicinal Chemistry and Pharmacognosy, Purdue University, West Lafayette, Indiana 47907.
Plant Physiol. 1991 Aug;96(4):1314-20. doi: 10.1104/pp.96.4.1314.
An auxin-stimulated NADH oxidase activity (NADH oxidase I) of plasma membrane vesicles, highly purified by aqueous two-phase partition from soybean (Glycine max Merr.) hypocotyls was activated by lysophospholipids and fatty acids, both products of phospholipase A action. The activation of NADH oxidase activity occurred slowly, suggesting a mechanism whereby the lipids acted to stabilize the enzyme in a more active configuration. In contrast to activation by lipids, the activation by auxin was rapid. The average K(m) of the NADH oxidase after activation by lipids was four- to fivefold less than the K(m) before activation. The V(max) was unchanged by activation. The increases occurred in the presence of detergent and thus were not a result of exposure of latent active sites. Also, the activation did not result from activation of a peroxidase or lipoxygenase. Fatty acid esters, where growth promoting effects have been reported, also activated the auxin-stimulated oxidase. However, the auxin stimulation of NADH oxidase I did not appear to be obligatorily mediated by phospholipase A, nor did inhibitors of phospholipase A(2) block the stimulation of the oxidase by auxins.
从大豆（Glycine max Merr.）下胚轴高度纯化的质膜囊泡中，通过双水相分配法刺激生长素刺激的 NADH 氧化酶活性（NADH 氧化酶 I），被溶血磷脂和脂肪酸激活，这两种物质都是磷脂酶 A 作用的产物。NADH 氧化酶活性的激活是缓慢发生的，这表明了一种机制，即脂质通过将酶稳定在更活跃的构象中来发挥作用。与脂质的激活相反，生长素的激活是快速的。经脂质激活后，NADH 氧化酶的平均 K(m) 比激活前的 K(m) 低四到五倍。V(max) 没有因激活而改变。这些增加是在去污剂存在的情况下发生的，因此不是潜伏活性位点暴露的结果。此外，激活不是由于过氧化物酶或脂氧合酶的激活。已报道具有生长促进作用的脂肪酸酯也能激活生长素刺激的氧化酶。然而，生长素对 NADH 氧化酶 I 的刺激似乎不必通过磷脂酶 A 介导，也没有磷脂酶 A(2)抑制剂阻止生长素对氧化酶的刺激。
