Mechanism of the Novel Prenylated Flavin-Containing Enzyme Ferulic Acid Decarboxylase Probed by Isotope Effects and Linear Free-Energy Relationships
作者:Kyle L. Ferguson、Nattapol Arunrattanamook、E. Neil G. Marsh
DOI:10.1021/acs.biochem.6b00170
日期:2016.5.24
Ferulic acid decarboxylase from Saccharomyces cerevisiae catalyzes the decarboxylation of phenylacrylic acid to form styrene using a newly described prenylated flavin mononucleotide cofactor. A mechanism has been proposed, involving an unprecedented 1,3-dipolar cyclo-addition of the prenylated flavin with the α═β bond of the substrate that serves to activate the substrate toward decarboxylation. We measured
来自酿酒酵母的阿魏酸脱羧酶使用新描述的异戊烯基黄素单核苷酸辅因子催化苯基丙烯酸的脱羧形成苯乙烯。已经提出了一种机制,涉及前所未有的将烯丙基黄素与底物的α═β键的1,3-偶极环加成,该底物的α3β键用于激活底物进行脱羧作用。我们测量了在苯基丙烯酸的α和β位置上的次级氘动力学同位素效应(KIE)与溶剂氘KIE的组合。溶剂KIE在V max / K M上为3.3,但在V max上接近于1,表明质子转移到产物发生在速率确定步骤之前。二次KIES是在α-和β-位置正常但在大小取决于反应是否H中进行变化2 O或d 2 O.在d 2 O,酶催化氘成苯乙烯的交换; 该反应取决于碳酸氢盐的存在。该观察结果暗示在产物质子化之后必须发生CO 2释放。通过使用一系列对位和间位取代的苯基丙烯酸,从反应的线性自由能分析中获得了更多信息。对数(k cat / K M)对于该反应与哈米特σ很好的相关性-参数用ρ= -0.39±0