Enzyme mediated reduction of 21-dehydrocorticosteroids at C-20: isolation and characterization of derivatives containing the 20beta-hydroxy-21-aldehyde side chain

Corticosteroid side chain oxidations--II. Metabolism of 20-dihydro steroids and evidence for steroid acid formation by direct oxidation at C-21

Rabbits have been injected with 4-14C-labelled progesterone, deoxycorticosterone and corticosterone and the corresponding 20 beta-3H-reduced steroids (20-dihydro steroids) in order to compare the influence of oxidation at C-20 on the excretion of steroid acids. Both 20 beta-reduced progesterone and deoxycorticosterone were extensively oxidized at C-20 and metabolized to 20-oxo-21-oic acids devoid of tritium. A small proportion of the acidic metabolites of [20 beta-3H]dihydro deoxycorticosterone retained tritium. By contrast the majority of the metabolites of [20 beta-3H]dihydro corticosterone were tritiated and [11 beta,20 beta-3H]-dihydroxy-4-pregnene-3-one-21-oic acid was identified as a major acidic metabolite. These results indicate that the presence of a 11 beta-hydroxyl in 20 beta-dihydro corticosterone inhibits oxidation at C-20 and provides evidence for the direct oxidation of this corticosteroid at C-21 in this species.

Oxidation of the 17-aldol (20 beta hydroxy-21-aldehyde) intermediate of corticosteroid metabolism to hydroxy acids by homogeneous human liver aldehyde dehydrogenases

In human liver, the oxidation of corticosteroids to 20-hydroxy-21-oic acids proceeds via the formation and oxidation of aldol (20-hydroxy-21-aldehyde) intermediates. Human liver aldehyde dehydrogenases E1 and E2, which we have previously purified to homogeneity, catalyzed the oxidation of the aldol isomer of cortisol (isocortisol) or of 11-deoxycorticosterone (isoDOC) by E1 and E2 respectively, were identified by the criteria of chromatographic mobility, derivatization, and reverse isotope dilution of 4-14C labeled acid end products. Both enzymes showed broad substrate specificity and oxidized both 17-hydroxy and 17-deoxy steroids, though at widely varying rates. Kinetic analysis of the course of oxidation of isocortisol and isoDOC by NAD+ gave intersecting initial velocity plots that conform with a sequential mechanism. The inhibition patterns for both enzymes with thionicotinamide adenine dinucleotide or chloral hydrate were consistent with random sequential behavior.