Ingelman-Sundberg M, Johansson I, Hansson A
Acta Biol Med Ger. 1979;38(2-3):379-88.
Two types of cytochrome P-450, P-450LM2 and P-450LM3, have been purified from rabbit liver microsomes and incorporated into phospholipid vesicles by a cholate gel filtration technique together with purified preparations of NADPH-cytochrome P-450 reductase. The catalytic properties of the vesicles have been compared with a system reconstituted with small amounts of dilauroylphosphatidylcholine (DLPC). 6 beta-Hydroxylation of androstenedione proceeded at a rate 10 times higher in the vesicles compared to the DLPC-system. The kinetics for the reaction were the same in the vesicles as in intact microsomes i.e. sigmoidal substrate curves were obtained and Hill-coefficients of about 1.4 were calculated in these systems. In contrast, Michaelis-Menten kinetics were obtained for 6 beta-hydroxylation in the DLPC-system. The results could indicate cooperativity between different P-450 molecules in the intact membrane but not in the DLPC-system. P-450LM2-catalyzed 16-hydroxylation of androstenedione was in contrast to the situation with P-450LM3 inhibited in the vesicles as compared to the DLPC system. It is suggested that for evaluation of substrate specificity and other properties of different types of liver microsomal P-450, phospholipid vesicles may be a more relevant integration level than the DLPC-system.
两种细胞色素P-450，即P-450LM2和P-450LM3，已从兔肝微粒体中纯化出来，并通过胆酸盐凝胶过滤技术与纯化的NADPH-细胞色素P-450还原酶制剂一起掺入磷脂囊泡中。已将这些囊泡的催化特性与用少量二月桂酰磷脂酰胆碱（DLPC）重构的系统进行了比较。与DLPC系统相比，雄烯二酮的6β-羟基化在囊泡中的进行速率高10倍。囊泡中该反应的动力学与完整微粒体中的相同，即获得了S形底物曲线，并且在这些系统中计算出的希尔系数约为1.4。相反，在DLPC系统中，6β-羟基化反应符合米氏动力学。结果表明，完整膜中不同的P-450分子之间存在协同作用，而在DLPC系统中则不存在。与DLPC系统相比，囊泡中P-450LM2催化的雄烯二酮16-羟基化受到抑制，这与P-450LM3的情况相反。有人提出，为了评估不同类型肝微粒体P-450的底物特异性和其他特性，磷脂囊泡可能比DLPC系统是更合适的整合水平。
