Stereochemistry of a bifunctional dihydroceramide Δ<sup>4</sup>-desaturase/hydroxylase from Candida albicans; a key enzyme of sphingolipid metabolism
作者:Christoph Beckmann、Janine Rattke、Petra Sperling、Ernst Heinz、Wilhelm Boland
DOI:10.1039/b303939k
日期:——
The stereochemical course of the dihydroceramide delta 4-(E)-desaturase from Candida albicans, cloned and expressed in the yeast Saccharomyces cerevisiae strain sur2 delta, was determined using stereospecifically labelled (2R,3S)-[2,3,4,4-2H4]-palmitic acid as a metabolic probe. Mass spectrometric analysis of the dinitrophenyl-derivatives of the labelled long-chain bases revealed elimination of a single
使用立体特异性标记的(2R,3S)-[2,3,4,4-确定了来自白色假丝酵母的二氢神经酰胺δ4-(E)-去饱和酶在啤酒酵母sur2 delta中克隆和表达的立体化学过程。 2H4]-棕榈酸作为代谢探针。标记的长链碱基的二硝基苯基衍生物的质谱分析表明,消除了C(4)(对应于C(4)-HR)的单个氘原子以及C(5)对应的氢原子(对应到C(5)-HS)。这一发现与两个邻位氢原子的整体同消相符。除了去饱和产物鞘氨醇(93%)以外,还鉴定出少量的4-羟基化产物(植物鞘氨醇,7%)将念珠菌酶分类为双功能去饱和酶/羟化酶。这两个过程 脱饱和和羟基化会伴随着手性前体的C(4)-HR损失。这一发现与两步过程一致,该过程涉及通过除去C(4)-HR来活化底物以产生C中心自由基或基团,然后歧化成烯烃,水和还原的二铁配合物,或使初级反应性中间体与活性位点结合的氧重组以产生仲醇。该结果证明了脱饱和和羟基化之间的紧密的