Département d'Enzymologie Cellulaire et Moléculaire, Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique UPR 406, 28, rue Goethe, F-67083 Strasbourg Cedex, France.
Plant Physiol. 1992 Oct;100(2):868-73. doi: 10.1104/pp.100.2.868.
Microsomes from etiolated wheat (Triticum aestivum L. cv Etoile de Choisy) shoots catalyzed the reduced nicotinamide adenine dinucleotide phosphate-dependent hydroxylation of lauric acid predominantly at the subterminal or (omega-1) position (65%). Minor amounts of 10-hydroxy- (31%) and 9-hydroxylaurate (4%) were also formed. The reaction was catalyzed by cytochrome P-450, since enzyme activity was strongly inhibited by tetcyclacis, carbon monoxide, and antibodies against NADPH-cytochrome c (P-450)-reductase. The apparent K(m) for lauric acid was estimated to be 8.5 +/- 2.0 mum. Seed treatment with the safener naphthalic acid anhydride or treatment of seedlings with phenobarbital increased cytochrome P-450 content and lauric acid hydroxylase (LAH) activity of the microsomes. A combination of both treatments further stimulated LAH activity. A series of radiolabeled unsaturated lauric acid analogs (8-, 9-, 10-, and 11-dodecenoic acids) was used to explore the regioselectivity and catalytic capabilities of induced wheat microsomes. It has been found that wheat microsomes catalyzed the reduced nicotinamide adenine dinucleotide phosphate-dependent epoxidation of sp2 carbons concurrently with hydroxylation at saturated positions. The regioselectivity of oxidation of the unsaturated substrates and that of lauric acid were similar. Preincubation of wheat microsomes with reduced nicotinamide adenine dinucleotide phosphate and 11-dodecenoic acid resulted in a partial loss of LAH activity.
小麦黄化苗微粒体催化还原型烟酰胺腺嘌呤二核苷酸磷酸依赖的月桂酸羟化作用，主要在亚末端或（ω-1）位置（65%）。还形成了少量的 10-羟基-（31%）和 9-羟基月桂酸（4%）。该反应由细胞色素 P-450 催化，因为酶活性强烈受到四环菌素、一氧化碳和针对 NADPH-细胞色素 c（P-450）-还原酶的抗体抑制。月桂酸的表观 K(m)估计为 8.5 +/- 2.0 mum。用安全剂萘酐处理种子或用苯巴比妥处理幼苗可增加微粒体中的细胞色素 P-450 含量和月桂酸羟化酶（LAH）活性。两种处理的结合进一步刺激了 LAH 活性。一系列放射性标记的不饱和月桂酸类似物（8-、9-、10-和 11-十二烯酸）被用于探索诱导的小麦微粒体的区域选择性和催化能力。已经发现，小麦微粒体催化 sp2 碳原子的还原型烟酰胺腺嘌呤二核苷酸磷酸依赖性环氧化作用，同时在饱和位置发生羟化作用。不饱和底物的氧化区域选择性与月桂酸的相似。用还原型烟酰胺腺嘌呤二核苷酸磷酸和 11-十二烯酸预孵育小麦微粒体导致 LAH 活性部分丧失。
