ENZYMATIC AROMATIZATION OF B RING OF DELTA5,7-STEROLS

1. 1. The sterols of Acanthamoeba castellanii (Neff) have been identified previously as the Δ5,7-sterols: ergosterol, 7-dehydroporiferasterol, 22,23-dihydroergosterol and 7-dehydroclionasterol. 2. 2. When homogenates of the amebas are incubated, the four sterols are enzymatically converted by loss of two hydrogen atoms to sterols with an aromatic Bring. It seems probable that the sterols retain the phenanthrene structure and that the aromatization is accompanied by a migration of the C-19 methyl group from C-10 to C-6 (or C-7). Thus, the product derived from ergosterol can tentatively be assigned the structure 6(7)-methylneoergosterol with homologous structures derived from the other three Δ5,7-sterols. 3. 3. As a consequence of these enzymatic reactions, 10-90% of the sterols of microsomes, mitochondria and plasma membrane are converted to the aromatic derivatives in the minimal time necessary for the isolation of the cell fractions. © 1969.