Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, P.O. Box 30, 420111 Kazan, Russia.
Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, P.O. Box 30, 420111 Kazan, Russia.
Biochim Biophys Acta Mol Cell Biol Lipids. 2020 Sep;1865(9):158743. doi: 10.1016/j.bbalip.2020.158743. Epub 2020 May 25.
The CYP74B subfamily of fatty acid hydroperoxide transforming cytochromes P450 includes the most common plant enzymes. All CYP74Bs studied yet except the CYP74B16 (flax divinyl ether synthase, LuDES) and the CYP74B33 (carrot allene oxide synthase, DcAOS) are 13-hydroperoxide lyases (HPLs, synonym: hemiacetal synthases). The results of present work demonstrate that additional products (except the HPL products) of fatty acid hydroperoxides conversion by the recombinant StHPL (CYP74B3, Solanum tuberosum), MsHPL (CYP74B4v1, Medicago sativa), and CsHPL (CYP74B6, Cucumis sativus) are epoxyalcohols. MsHPL, StHPL, and CsHPL converted the 13-hydroperoxides of linoleic (13-HPOD) and α-linolenic acids (13-HPOT) primarily to the chain cleavage products. The minor by-products of 13-HPOD and 13-HPOT conversions by these enzymes were the oxiranyl carbinols, 11-hydroxy-12,13-epoxy-9-octadecenoic and 11-hydroxy-12,13-epoxy-9,15-octadecadienoic acid. At the same time, all enzymes studied converted 9-hydroperoxides into corresponding oxiranyl carbinols with HPL by-products. Thus, the results showed the additional epoxyalcohol synthase activity of studied CYP74B enzymes. The 13-HPOD conversion reliably resulted in smaller yields of the HPL products and bigger yields of the epoxyalcohols compared to the 13-HPOT transformation. Overall, the results show the dualistic HPL/EAS behaviour of studied CYP74B enzymes, depending on hydroperoxide isomerism and unsaturation.
CYP74B 亚家族的脂肪酸氢过氧化物转化细胞色素 P450 包括最常见的植物酶。迄今为止，除了 CYP74B16（亚麻二乙烯醚合酶，LuDES）和 CYP74B33（胡萝卜丙二烯氧化物合酶，DcAOS）之外，所有研究过的 CYP74B 都是 13-氢过氧化物裂解酶（HPL，同义词：半缩醛合酶）。本工作的结果表明，重组 StHPL（CYP74B3，马铃薯）、MsHPL（CYP74B4v1，紫花苜蓿）和 CsHPL（CYP74B6，黄瓜）转化脂肪酸氢过氧化物的额外产物（除 HPL 产物外）为环氧化醇。MsHPL、StHPL 和 CsHPL 主要将亚油酸（13-HPOD）和α-亚麻酸（13-HPOT）的 13-氢过氧化物转化为链断裂产物。这些酶转化 13-HPOD 和 13-HPOT 的次要副产物为环氧化甲醇，即 11-羟基-12,13-环氧-9-十八烯酸和 11-羟基-12,13-环氧-9,15-十八碳二烯酸。同时，所有研究的酶均将 9-氢过氧化物转化为相应的环氧化甲醇和 HPL 副产物。因此，研究结果表明所研究的 CYP74B 酶具有额外的环氧化醇合酶活性。与 13-HPOT 转化相比，13-HPOD 转化可靠地导致 HPL 产物的产量较小，而环氧化醇的产量较大。总的来说，研究结果表明所研究的 CYP74B 酶具有双重 HPL/EAS 行为，这取决于氢过氧化物的异构化和不饱和度。
