Organ-specific properties of cytochromes P-450s21 (steroid 21-hydroxylases) of liver and adrenocortical microsomes.

Organ specificities of cytochrome P-450s21 (steroid 21-hydroxylase) were investigated. The substrate specificity of the liver cytochrome P-450s21 was found to be different from that of adrenocortical cytochrome P-450s21. The steroid 21-hydroxylase activity of liver microsomes decreased with treatment by sodium phenobarbital or beta-naphthoflavone and was inhibited by anti-cytochrome b5 immunoglobulin, although that of adrenocortical microsomes was not. The liver cytochrome P-450s21 was immunochemically similar to adrenocortical cytochrome P-450s21. The bovine liver and adrenocortical cytochromes P-450s21 showed immunoprecipitin lines against antibody to bovine adrenocortical cytochrome P-450s21. The molecular masses of the bovine liver and adrenocortical cytochromes P-450s21 were 60 +/- 1 and 50 +/- 1 kDa, respectively. The content of cytochrome P-450s21 and its percentage for the total microsomal cytochrome P-450 were immunochemically determined using the antibody to the bovine adrenocortical cytochrome P-450s21.