Isolation of Two Distinct Cytochromes P-450_11β with Aldosterone Synthase Activity from Bovine Adrenocortical Mitochondria

Abstract

Two distinct forms of cytochrome P-450_11β, with apparent molecular weights of 48, 500 (48.5K) and 49, 500 (49.5K), have been isolated from bovine adrenocortical mitochondria. Their amino acid sequences up to the 19th position from the N-terminus were only different at the 6th position (Val and Ala for the 48.5K and 49.5K enzymes, respectively). Each sequence was assignable to a distinct cDNA clone for cytochrome P-450_11β (Kirita, S., et al. [1988] J. Biochem. 104, 683-686), indicating that the two proteins originate from different genes in bovine adrenocortical cells. Both forms of cytochrome P-450_11β were capable of catalyzing aldosterone synthesis as well as the 11β- and 18-hydroxylation of 11-deoxycorticosterone. Thus, at least two distinct cytochrome P-450_11β species exist in the adrenal cortex and participate in steroidogenesis.