Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States.
J Am Chem Soc. 2015 Apr 22;137(15):4940-3. doi: 10.1021/jacs.5b01965. Epub 2015 Apr 10.
OleT(JE), a cytochrome P450, catalyzes the conversion of fatty acids to terminal alkenes using hydrogen peroxide as a cosubstrate. Analytical studies with an eicosanoic acid substrate show that the enzyme predominantly generates nonadecene and that carbon dioxide is the one carbon coproduct of the reaction. The addition of hydrogen peroxide to a deuterated substrate-enzyme (E-S) complex results in the transient formation of an iron(IV) oxo π cation radical (Compound I) intermediate which is spectroscopically indistinguishable from those that perform oxygen insertion chemistries. A kinetic isotope effect for Compound I decay suggests that it abstracts a substrate hydrogen atom to initiate fatty acid decarboxylation. Together, these results indicate that the initial mechanism for alkene formation, which does not result from oxygen rebound, is similar to that widely suggested for P450 monooxygenation reactions.
OleT(JE) 是一种细胞色素 P450，它使用过氧化氢作为共底物将脂肪酸催化转化为末端烯烃。对二十烷酸底物的分析研究表明，该酶主要生成十九烯，并且二氧化碳是反应的一碳副产物。向氘代底物-酶 (E-S) 复合物中添加过氧化氢会导致铁 (IV) 氧π阳离子自由基 (化合物 I) 中间体的瞬时形成，该中间体在光谱上与进行氧插入化学的那些中间体无法区分。化合物 I 衰减的动力学同位素效应表明，它会夺取底物的一个氢原子以启动脂肪酸脱羧反应。综上所述，这些结果表明，烯烃形成的初始机制不是由于氧回弹引起的，与广泛认为的 P450 单加氧反应的机制相似。
