Electron Transport Components of Hepatic Microsomes

Components of the hepatic microsomal P-450 hemoprotein electron transfer system (TPNH-cytochrome c reductase and P-450 hemoprotein) and the microsomal cytochrome b5 electron transfer system (DPNH-cytochrome b5 reductase and cytochrome b5) were solubilized using Triton N-101 and glycerol, and separated using DEAE-cellulose chromatography. Microsomal aniline hydroxylase activity was reconstituted when the TPNH-cytochrome c reductase fractions and the P-450 hemoprotein fraction were combined. Cross-activities of the TPNH reductases and P-450 hemoproteins were obtained with preparations from phenobarbital- and 3-methylcholanthrene-treated rats. The reconstituted aniline hydroxylase system resembled the native system with respect to turnover number, reducibility of the P-450 hemoprotein component with TPNH, and inhibition with carbon monoxide, p-chloromercuribenzoate, and vitamin K3, but differed in its ability to react with type I substrates such as ethylmorphine and aminopyrine.