Biochemistry and Biophysics Section, University of Connecticut, Storrs, Connecticut 06268.
Plant Physiol. 1980 Jan;65(1):107-13. doi: 10.1104/pp.65.1.107.
Indoleacetaldehyde reductase catalyzes the conversion of indoleacetaldehyde to indole ethanol in extracts of Cucumis sativus L., with reduced pyridine nucleotide required as co-substrate. NADH and NADPH result in markedly different enzyme behavior, as reflected in reaction kinetics and in responses to inhibitors and activators. It is not yet clear whether there are two separate enzymes, one specific for NADH and the other for NADPH, or whether there is a single enzyme differentially influenced by the two co-substrates.In the presence of NADH, the indoleacetaldehyde reductase activity was inhibited by NaCl and displayed hyperbolic kinetics under all conditions tested. However, in the presence of NADPH the enzyme was activated by NaCl at concentrations up to 0.1 molar. Under certain conditions with NADPH as co-substrate, the enzyme showed kinetics sigmoidal with respect to indoleacetaldehyde concentration and was strongly inhibited by high concentrations of NADPH. It is possible that this substrate inhibition of the NADPH-linked indoleacetaldehyde reductase activity by NADPH, as well as the sigmoidicity with respect to indoleacetaldehyde concentration, may function in the regulation of auxin biosynthesis.
色氨乙醛还原酶在黄瓜提取物中催化色氨乙醛转化为色氨乙醇，需要还原型吡啶核苷酸作为辅酶。NADH 和 NADPH 导致明显不同的酶行为，这反映在反应动力学以及对抑制剂和激活剂的反应上。目前尚不清楚是否存在两种分离的酶，一种特异性地作用于 NADH，另一种特异性地作用于 NADPH，或者是否存在一种单一的酶，其被两种辅酶不同地影响。在 NADH 存在的情况下，色氨乙醛还原酶的活性被 NaCl 抑制，并且在所有测试条件下均表现出双曲线动力学。然而，在 NADPH 存在的情况下，酶在高达 0.1 摩尔的浓度下被 NaCl 激活。在 NADPH 作为辅酶的某些条件下，酶对色氨乙醛浓度表现出 S 形动力学，并且被高浓度的 NADPH 强烈抑制。可能是 NADPH 对 NADPH 连接的色氨乙醛还原酶活性的这种底物抑制，以及对色氨乙醛浓度的 S 形性，可能在生长素生物合成的调节中起作用。
