A study of steroid 11beta-hydroxylation by adrenal mitochondria of marsupials--Part II. the effect of corticotrophin, metopirone and pH on 11beta-hydroxylation of 11-deoxycortisol and 17alpha-oh-progesterone by adrenal mitochondria of possum (Trichosurus vulpecula)

Vardolov, L.; Weiss, M.

Journal of Steroid Biochemistry 9(1): 47-52


ISSN/ISBN: 0022-4731
PMID: 24136
DOI: 10.1016/0022-4731(78)90101-2
Accession: 068518316

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ACTH administration to possum caused an increase in adrenal weight and in mitochondrial protein. Compared with untreated animals, the KM for 11.beta.-hydroxylation of 11-deoxycortisol (S) and 17.alpha.-OH-progesterone (17OHP) after ACTH treatment decreased for both substrates, by approximately 2.6 times and V increased by approximately 3.6 times. Simultaneous addition of S and 17OHP acting as alternate inhibitors, showed a mutual competitive inhibition of 11.beta.-hydroxylation, the percent inhibition being the same before and after ACTH treatment. The effect of pH on 11.beta.-hydroxylation of S and 17OHP over a range of 6.2-9.5 indicated a similar pattern of change with optima at approximately pH 8 for both substrates. Addition of metopirone competitively inhibited the 11.beta.-hydroxylation of S and 17OHP, which at equimolar concentrations, was for both substrates 38%. A single non-substrate-specific 11.beta.-hydroxylase enzyme operates in marsupials.