Behrends W, Thieringer R, Engeland K, Kunau W H, Kindl H
Universität Marburg, Federal Republic of Germany.
Arch Biochem Biophys. 1988 May 15;263(1):170-7. doi: 10.1016/0003-9861(88)90625-x.
Fat-degrading cotyledons from cucumber seedlings were investigated with respect to the enzymes metabolizing cis-unsaturated fatty acids. Isolated glyoxysomes degrade linoleic acid, the dominating fatty acid in the storage tissue of the seed. Glyoxysomes were shown to be the sole intracellular site of enzymes responsible for the degradation of unsaturated fatty acids. All three auxiliary enzyme activities discussed for the degradation of polyunsaturated fatty acids, 2,4-dienoyl-CoA reductase, enoyl-CoA isomerase, and 3-hydroxyacyl-CoA epimerase were localized within the matrix of glyoxysomes. They were not found in mitochondria. Separation of glyoxysomal matrix proteins on CM-cellulose revealed that epimerase activity was attributable to the multifunctional protein and also to another protein which apparently exhibited no other beta-oxidation activity. Furthermore, on the basis of the high epimerase activity present in glyoxysomes compared to a much lower 2,4-dienoyl-CoA reductase activity, the metabolism of unsaturated fatty acids via delta 2-cis-enoyl-CoA is considered as alternative to the reductase-dependent pathway.
对黄瓜幼苗中降解脂肪的子叶进行了研究，以探讨代谢顺式不饱和脂肪酸的酶。分离出的乙醛酸循环体可降解亚油酸，亚油酸是种子储存组织中的主要脂肪酸。已证明乙醛酸循环体是负责不饱和脂肪酸降解的酶的唯一细胞内位点。讨论的用于多不饱和脂肪酸降解的所有三种辅助酶活性，即2,4-二烯酰辅酶A还原酶、烯酰辅酶A异构酶和3-羟酰基辅酶A差向异构酶，都定位于乙醛酸循环体的基质中。在 mitochondria 中未发现它们。在CM-纤维素上分离乙醛酸循环体基质蛋白表明，差向异构酶活性可归因于多功能蛋白，也可归因于另一种显然没有其他β-氧化活性的蛋白。此外，基于乙醛酸循环体中存在的高差向异构酶活性与低得多的2,4-二烯酰辅酶A还原酶活性相比，通过δ2-顺式烯酰辅酶A的不饱和脂肪酸代谢被认为是还原酶依赖性途径的替代途径。
