Sperling P, Zähringer U, Heinz E
Institut für Allgemeine Botanik, Universität Hamburg, Ohnhorststrasse 18, D-22609 Hamburg, Germany.
J Biol Chem. 1998 Oct 30;273(44):28590-6. doi: 10.1074/jbc.273.44.28590.
A recently cloned cDNA from sunflower codes for a fusion protein composed of an N-terminal cytochrome b5 and a domain similar to membrane-bound acyl lipid desaturases. For a functional identification, homologous cDNAs from Brassica napus and Arabidopsis thaliana were expressed in Saccharomyces cerevisiae, and sphingolipid long chain bases were analyzed. The expression of the heterologous enzyme results in significant proportions of new Delta8, 9-cis/trans-phytosphingenines that accompany the residual C18-phytosphinganine predominating in wild-type yeast cells. These results represent the first identification of a gene coding for a sphingolipid desaturase and for a stereounselective desaturase showing trans-activity from any organism. Furthermore, this fusion protein is a new member of the cytochrome b5 superfamily. The formation of the two regioisomeric phytosphingenines in the transformed yeast sheds new light on the factors controlling regioselectivity.
最近从向日葵中克隆出的一个cDNA编码一种融合蛋白，该蛋白由一个N端细胞色素b5和一个类似于膜结合酰基脂质去饱和酶的结构域组成。为了进行功能鉴定，将来自甘蓝型油菜和拟南芥的同源cDNA在酿酒酵母中表达，并对鞘脂长链碱进行分析。异源酶的表达导致了大量新的Δ8,9-顺式/反式植物鞘氨醇的产生，这些新的植物鞘氨醇伴随着野生型酵母细胞中占主导地位的残留C18-植物鞘氨醇。这些结果首次鉴定了一个编码鞘脂去饱和酶和一种具有反式活性的立体非选择性去饱和酶的基因，该酶来自任何生物体。此外，这种融合蛋白是细胞色素b5超家族的一个新成员。在转化酵母中两种区域异构体植物鞘氨醇的形成，为控制区域选择性的因素提供了新的线索。
