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脂肪酸氢过氧化物转化细胞色素P450的亚家族包括最常见的植物酶。除CYP74B16（亚麻二乙烯基醚合酶，LuDES）和CYP74B33（胡萝卜丙二烯氧化合酶，DcAOS）外，所有已研究的CYP74B均为13-氢过氧化物裂解酶（HPL，同义词：半缩醛合酶）。当前工作的结果表明，通过重组StHPL（CYP74B3，马铃薯），MsHPL（CYP74B4v1，紫花苜蓿）和CsHPL（CYP74B6，Cucumis sativus）转化脂肪酸氢过氧化物的其他产品（HPL产品除外））是环氧醇。MsHPL，StHPL和CsHPL将亚油酸（13-HPOD）和α-亚麻酸（13-HPOT）的13-氢过氧化物主要转化为链断裂产物。这些酶的13-HPOD和13-HPOT转化的次要副产物是环氧乙烷基甲醇，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-氢过氧化物与HPL副产物转化为相应的环氧乙烷基甲醇。因此，结果表明所研究的CYP74B酶具有额外的环氧醇合酶活性。与13-HPOT转化相比，13-HPOD转化可靠地导致HPL产品的收率降低，环氧醇的收率更高。总体而言，结果表明所研究的CYP74B酶具有双重HPL / EAS行为，