Reed J R, Quilici D R, Blomquist G J, Reitz R C
Department of Biochemistry, University of Nevada, Reno 89557-0014, USA.
Biochemistry. 1995 Dec 12;34(49):16221-7. doi: 10.1021/bi00049a038.
Experiments were performed to elucidate the mechanism of hydrocarbon formation in microsomal preparations from the house fly, Musca domestica. Antibody to both house fly cytochrome P450 reductase and a purified cytochrome P450 (CYP6A1) from the house fly inhibited (Z)-9-tricosene (Z9-23:Hy) formation from [15,16-3H]-(Z)-15-tetracosenal (24:1 aldehyde). Chemical ionization-gas chromatography-mass spectrometry (CI-GC-MS) analyses of the n-tricosane formed by microsomal preparations from [2,2-2H2,2-13C]- and [3,3-2H2,3-13C]tetracosanoyl-CoA demonstrated that the deuteriums on the 2,2- and 3,3-positions were retained in the conversion to the hydrocarbon product. Likewise, CI-GC-MS analysis of the Z9-23:Hy formed from [1-2H]tetracosenal by microsomal preparations demonstrated that the aldehydic proton on the 1-carbon was transferred to the hydrocarbon product. Hydrogen peroxide, cumene hydroperoxide, and iodosobenzene were able to support hydrocarbon production from [3H]24:1 aldehyde in place of O2 and NADPH for short incubation times. From these data, a cytochrome P450 mechanism is proposed in which the perferryl iron-oxene, resulting from heterolytic cleavage of the O-O bond of the iron-peroxy intermediate, abstracts an electron from the C=O double bond of the carbonyl group of the aldehyde. The reduced perferryl attacks the 1-carbon of the aldehyde to form a thiyl-iron-hemiacetal diradical. The latter intermediate can fragment to form an alkyl radical and a thiyl-iron-formyl radical. The alkyl radical then abstracts the formyl hydrogen to produce the hydrocarbon and CO2.
进行了实验以阐明家蝇（Musca domestica）微粒体制剂中碳氢化合物形成的机制。针对家蝇细胞色素P450还原酶和纯化的家蝇细胞色素P450（CYP6A1）的抗体抑制了[15,16-³H]-(Z)-15-二十四碳烯醛（24:1醛）形成(Z)-9-二十三碳烯（Z9-23:Hy）。对由[2,2-²H₂,2-¹³C]-和[3,3-²H₂,3-¹³C]二十四碳酰辅酶A的微粒体制剂形成的正二十三烷进行化学电离-气相色谱-质谱（CI-GC-MS）分析表明，2,2-和3,3-位上的氘在转化为碳氢化合物产物时得以保留。同样，对微粒体制剂由[1-²H]二十四碳烯醛形成的Z9-23:Hy进行CI-GC-MS分析表明，1-碳上的醛基质子转移到了碳氢化合物产物上。在短时间孵育时，过氧化氢、异丙苯过氧化氢和亚碘酰苯能够替代O₂和NADPH支持从[³H]24:1醛产生碳氢化合物。根据这些数据，提出了一种细胞色素P450机制，其中铁-过氧中间体的O-O键异裂产生的高铁氧烯从醛羰基的C=O双键夺取一个电子。还原的高铁氧烯攻击醛的1-碳形成硫基-铁-半缩醛双自由基。后一种中间体可裂解形成烷基自由基和硫基-铁-甲酰基自由基。然后烷基自由基夺取甲酰基氢以产生碳氢化合物和CO₂。
