CLONING AND EXPRESSION OF A CDNA FOR HUMAN CYTOCHROME-P-450ALDO AS RELATED TO PRIMARY ALDOSTERONISM

A cDNA clone encoding human aldosterone synthase cytochrome P-450 (P-450aldo) has been isolated from a cDNA library derived from human adrenal tumor of a patient suffering from primary aldosteronism. The insert of the clone contains an open reading frame encoding a protein of 503 amino acid residues together with a 3 bp 5′-untranslated region and a 1424 bp 3′-untranslated region to which a poly(A) tract is attached. The nucleotide sequence of P-450aldo cDNA is 93% identical to that of P-45011β cDNA. Catalytic functions of these two P-450s expressed in COS-7 cells are very similar in that both enzymes catalyze the formation of corticosterone and 18-hydroxy-11-deoxycorticosterone using 11-deoxycorticosterone as a substrate. However, they are distinctly different from each other in that P-450aldo preferentially catalyzes the conversion of 11-deoxycorticosterone to aldosterone via corticosterone and 18-hydroxycorticosterone while P-45011β substantially fails to catalyze the reaction to form aldosterone. These results suggest that P-450aldo is a variant of P-45011β, but this enzyme is a different gene product possibly playing a major role in the synthesis of aldosterone at least in a patient suffering from primary aldosteronism. © 1990 Academic Press, Inc.