Biochemistry-Physiology Group, State University of New York College of Environmental Science and Forestry, Syracuse, New York 13210.
Plant Physiol. 1976 Dec;58(6):790-5. doi: 10.1104/pp.58.6.790.
A cell-free enzyme system capable of metabolizing abscisic acid has been obtained from Eastern Wild Cucumber (Echinocystis lobata Michx.) liquid endosperm. The reaction products were determined to be phaseic acid (PA) and dihydrophaseic acid (DPA) by co-chromatography on thin layer chromatograms as the free acids, methyl esters, and their respective oxidation or reduction products. The crude enzyme preparation was separated by centrifugation into a particulate abscisic acid (ABA)-hydroxylating activity and a soluble PA-reducing activity. The particulate ABA-hydroxylating enzyme showed a requirement for O(2) and NADPH, inhibition by CO, and high substrate specificity for (+)-ABA. Acetylation of short term incubation mixtures gave evidence for the presence of 6'-hydroxymethyl-ABA as an intermediate in PA formation. Determinations of endogenous ABA and DPA concentrations suggest that the ABA-hydroxylating and PA-reducing enzymes are extensively metabolizing ABA in the intact E. lobata seed.
已从东方野西瓜（Echinocystis lobata Michx.）液体胚乳中获得一种能够代谢脱落酸的无细胞酶系统。通过在薄层色谱上的共色谱分析，将反应产物鉴定为游离酸、甲酯及其各自的氧化或还原产物，即法呢基酸（PA）和二氢法呢基酸（DPA）。粗酶制剂通过离心分离成颗粒状脱落酸（ABA）羟化酶和可溶性 PA 还原酶。颗粒状 ABA 羟化酶需要 O(2)和 NADPH，被 CO 抑制，对（+）-ABA 具有高底物特异性。短期孵育混合物的乙酰化证明 6'-羟甲基-ABA 作为 PA 形成的中间产物存在。内源性 ABA 和 DPA 浓度的测定表明，ABA 羟化酶和 PA 还原酶在完整的 E. lobata 种子中广泛代谢 ABA。
