Borgeson C E, de Renobales M, Blomquist G J
Department of Biochemistry, University of Nevada, Reno 89557.
Biochim Biophys Acta. 1990 Nov 12;1047(2):135-40. doi: 10.1016/0005-2760(90)90039-z.
The cockroach, Periplaneta americana, can convert oleic acid (18:1(n - 9], to linoleic acid, (18:2(n - 6], by a microsomal delta 12 desaturase. Most of the desaturase activity was present in the fat body tissue, with lower activity in the epidermis and no detectable activity in the thorax or gut tissue. In incubations of microsomal preparations from fat body tissues with [1-14C]18:1-CoA, increased amounts of [1-14C]18:2 were found with increasing time and protein concentration. The form of the substrate for the delta 12 desaturase was determined to be 18:1-CoA by comparing activity towards [1-14C]18:1-CoA and [1-14C]18:1 transesterified to phospholipid. Ozonolysis of the 18:2 formed from [1-14C]oleoyl-CoA followed by radio-gas-liquid chromatography gave one labeled peak, 9-oxononanoate, which showed that the product of the delta 12 desaturase is the physiologically important isomer, 18:2(n - 6).
美洲大蠊能够通过微粒体Δ12去饱和酶将油酸（18:1(n - 9)）转化为亚油酸（18:2(n - 6)）。大部分去饱和酶活性存在于脂肪体组织中，表皮中的活性较低，而在胸部或肠道组织中未检测到活性。在用[1-14C]18:1-辅酶A对脂肪体组织的微粒体制剂进行孵育时，随着时间和蛋白质浓度的增加，[1-14C]18:2的量也增加。通过比较对[1-14C]18:1-辅酶A和转酯化为磷脂的[1-14C]18:1的活性，确定Δ12去饱和酶的底物形式为18:1-辅酶A。对由[1-14C]油酰辅酶A形成的18:2进行臭氧分解，然后进行放射性气-液色谱分析，得到一个标记峰，即9-氧代壬酸，这表明Δ12去饱和酶的产物是具有生理重要性的异构体18:2(n - 6)。
