Herman C A, Oliw E H
Department of Biology, New Mexico State University, Las Cruces 88003, USA.
J Exp Zool. 1998 Jan 1;280(1):1-7. doi: 10.1002/(sici)1097-010x(19980101)280:1<1::aid-jez1>3.0.co;2-s.
Polyunsaturated fatty acids (PUFAs) can be oxygenated by mammalian hepatic P450s to a series of metabolites. The most prominent of these are formed by omega- and (omega-1)-hydroxylation, epoxidation of the double bonds or bisallylic hydroxylation. The object of the present investigation was to determine whether similar oxygenations are catalyzed by liver microsomes of the yellow rat snake (Elaphe obsoleta) and the American bullfrog (Rana catesbeiana). Liver microsomes were incubated with [1-14C]-labeled arachidonic (AA), eicosapentaenoic (EPA), and linoleic acids (LA) in the presence or absence of 1 mM NADPH, and the major metabolites were analyzed by reverse-phase and straight-phase high performance liquid chromatography and capillary gas chromatography-mass spectroscopy. No metabolites were produced in the absence of NADPH. Profiles of metabolites were different depending on the organism and the acclimation state. In all incubations, EPA was the most effective substrate utilized and LA the least effective. The major products from EPA were 19-HEPE, 13-HEPE, and 20-HEPE from cold-acclimated (5 degrees C), warm-acclimated (22 degrees C) frogs, and snakes (22 degrees C), respectively. In contrast, 20-HETE production from AA was greater than 19-HETE in all three. Cold-acclimated frog liver microsomes produced significantly more of all metabolites when compared with microsomes from warm-acclimated frogs. We conclude that amphibian and snake liver can catalyze epoxidation and hydroxylation of PUFAs and that products are species-specific and acclimation-state dependent.
多不饱和脂肪酸（PUFAs）可被哺乳动物肝脏中的细胞色素P450氧化为一系列代谢产物。其中最主要的是通过ω-和（ω-1）-羟基化、双键环氧化或双烯丙基羟基化形成的代谢产物。本研究的目的是确定黄锦蛇（Elaphe obsoleta）和美国牛蛙（Rana catesbeiana）的肝脏微粒体是否能催化类似的氧化反应。在有或没有1 mM NADPH存在的情况下，将肝脏微粒体与[1-14C]标记的花生四烯酸（AA）、二十碳五烯酸（EPA）和亚油酸（LA）一起孵育，然后通过反相和正相高效液相色谱以及毛细管气相色谱-质谱分析主要代谢产物。在没有NADPH的情况下未产生代谢产物。代谢产物的谱图因生物体和适应状态而异。在所有孵育实验中，EPA是最有效的被利用底物，而LA是最无效的。来自EPA的主要产物分别是来自冷适应（5摄氏度）、热适应（22摄氏度）的青蛙以及蛇（22摄氏度）的19-羟基二十碳五烯酸（19-HEPE）、13-羟基二十碳五烯酸（13-HEPE）和20-羟基二十碳五烯酸（20-HEPE）。相比之下，在所有这三种情况下，由AA产生的20-羟基二十碳四烯酸（20-HETE）都比19-羟基二十碳四烯酸（19-HETE）多。与热适应青蛙的微粒体相比，冷适应青蛙的肝脏微粒体产生的所有代谢产物都明显更多。我们得出结论，两栖动物和蛇的肝脏能够催化PUFAs的环氧化和羟基化反应，并且产物具有物种特异性且依赖于适应状态。
