Bacterial formation of aldosterone metabolites.

The experiments described in this paper demonstrate that most of the metabolic alterations of the aldosterone molecule, hitherto attributed to hepatic enzymes, equally well may be carried out by enzymes synthesized by anaerobic bacteria from the human gut. The steroid reductases synthesized by Clostridium paraputrificum, Clostridium J-1, and Clostridium innocuum convert aldosterone to the 3 alpha, 5 beta tetrahydroaldosterone (THA), 3 beta, 5 alpha-THA, and 3 alpha, 5 alpha-THA, respectively. All three enzymes metabolize 5 alpha.dihydroaldosterone to a single compound: 3 beta, 5 alpha-THA. Bifidobacterium adolescentis reduces aldosterone to 20 beta-dihydroaldosterone. In mixed cultures of B. adolescentis and clostridia, the individual enzymes operate independently of each other; however, about half of the aldosterone metabolites are in the free form and half in the acetal form. By appropriate selection of substrate and bacterial strains, therefore, it is possible to biosynthesize not only three of the THA isomers but also the hexahydroisomers in free form as well as in the acetal form.