19-Hydroxylase inhibition of adrenal mitochondrial P450 11 beta/18/19-hydroxylase by a suicide inhibitor.
19-Nor-deoxycorticosterone (19-nor-DOC) is a mineralocorticoid that is increased in some forms of experimental and human hypertension. The pivotal step in 19-nor-DOC biosynthesis is adrenal P450 19-hydroxylase, but this enzyme has not been clearly distinguished from P450 11 beta/18-hydroxylase. This study attempted to specifically inhibit adrenal 19-hydroxylation of deoxycorticosterone (DOC) using a suicide aromatase inhibitor, 19-acetylenic androstenedione (19-AA). Purified bovine P450 11 beta/18/19-hydroxylase was incubated with excess substrate DOC, adrenodoxin, and adrenodoxin reductase in the presence of increasing doses of the inhibitor, 19AA. 11 beta-, 18-, and 19-hydroxylation were measured by quantification of corticosterone, 18-OH-DOC, and 19-OH-DOC respectively. Measurements of these products demonstrated that 11 beta- and 18-hydroxylation was not inhibited whereas 19-hydroxylation was inhibited as manifested by decreased 19-OH-DOC formation (p less than .05). The IC50 of 19-AA was approximately 10(-12) M. The specific inhibition of 19-hydroxylation suggests that the 19-hydroxylase may be an enzyme distinct from the P450 11 beta/18-hydroxylase. This further suggests that 19-nor-DOC biosynthesis may be under independent regulation and may be amendable to specific in vivo inhibition.
Griffing
G T
GT
Evans Memorial Department of Clinical Research, University Hospital, Boston, Massachusetts 02118.
Holbrook
M
M
Melby
J C
JC
Alberta
J
J
Orme-Johnson
N R
NR
D000311:Adrenal Glands / Q000201:enzymology*; D000325:Adrenodoxin; D000735:Androstenedione / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D019405:Cytochrome P-450 CYP11B2; D065607:Cytochrome P-450 Enzyme Inhibitors; D003900:Desoxycorticosterone / Q000031:analogs & derivatives / Q000096:biosynthesis; D005287:Ferredoxin-NADP Reductase; D006900:Hydroxylation; D066298:In Vitro Techniques; D008928:Mitochondria / Q000201:enzymology*; D010293:Pargyline / Q000031:analogs & derivatives* / Q000494:pharmacology; D013252:Steroid 11-beta-Hydroxylase / Q000037:antagonists & inhibitors; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors*
D065607:Cytochrome P-450 Enzyme Inhibitors; D000325:Adrenodoxin; D000735:Androstenedione; D003900:Desoxycorticosterone; C019026:19-nordeoxycorticosterone; D010293:Pargyline; D013250:Steroid Hydroxylases; C027110:steroid 19-hydroxylase; D019405:Cytochrome P-450 CYP11B2; D013252:Steroid 11-beta-Hydroxylase; D005287:Ferredoxin-NADP Reductase; C033071:plomestane