Lipscomb J D, Sligar S G, Namtvedt M J, Gunsalus I C
J Biol Chem. 1976 Feb 25;251(4):1116-24.
Oxy-ferrous substrate-bound cytochrome P-450cam (mrsO2) autooxidizes in the absence of its specific effector protein, putidaredoxin, without hydroxylating the substrate, camphor. The autooxidation is first order with an activation energy of 17 kcal mol-1 at 25 degrees, pH 7.0. Substrate removal and low pH accelerate the reaction. The product, 5-exo-OH camphor, and a nonhydroxylated pseudosubstrate, norcamphor, stabilize the complex in a manner similar to camphor. Increased oxidation rate of mrsO2 and substrate hydroxylation are induced by putidaredoxin, rebredoxin, cytochrome b5, and the apoproteins of the latter two. Dihydrolipoic acid and other dithiols also replace putidaredoxin as effector molecules, but 1000-fold higher concentrations are required. Effector molecules do not increase the autooxidation rate of mrsO2 unless camphor, norcamphor, or another pseudosubstrate is present. Kinetic evidence is presented showing that an active complex between mrsO2 and effector is a required intermediate in mixed function oxidation.
与亚铁底物结合的细胞色素P-450cam（mrsO2）在没有其特异性效应蛋白恶臭假单胞菌铁氧还蛋白的情况下会自动氧化，且不会使底物樟脑羟基化。在25摄氏度、pH值为7.0时，自动氧化反应为一级反应，活化能为17千卡/摩尔。去除底物和低pH值会加速该反应。产物5-外向-羟基樟脑和一种非羟基化的假底物降樟脑，以类似于樟脑的方式稳定该复合物。恶臭假单胞菌铁氧还蛋白、重组铁氧还蛋白、细胞色素b5以及后两者的脱辅基蛋白可诱导mrsO2的氧化速率增加和底物羟基化。二氢硫辛酸和其他二硫醇也可替代恶臭假单胞菌铁氧还蛋白作为效应分子，但所需浓度要高1000倍。除非存在樟脑、降樟脑或其他假底物，否则效应分子不会增加mrsO2的自动氧化速率。动力学证据表明，mrsO2与效应分子之间的活性复合物是混合功能氧化中必需的中间体。
