Microbial degradation of 19-hydroxy-sterol side chains

Experimental evidence is herein presented to show that C₂₂ acids are key intermediates in the microbial degradation of cholesterol and campesterol (β-sitosterol) side chains. Exposure of 19-hydroxy-sterols to Rhodococcus mutant K-3 gave four new steroid carboxylic acids in addition to that known as estrone (P1); the chemical structures of these metabolites were characterized as 2(3-hydroxy-1,3,5(10)-estratrien-17-yl)-propionic acid (P2), 2-methyl-6(3-hydroxy-1,3,5(10)-estratrien-17-yl)-heptanoic acid (P3), 2,3-dimethyl-6(3-hydroxy-1,3,5(10)-estratrien-17-yl)-heptanoic acid (P4), and 2(3-hydroxy-1,3,5(10), 17-estratetraen-17-yl)-propionic acid (P5). We propose a degradation pathway of 19-hydroxy-cholesterol and campesterol (β-sitosterol) side chains.