Biotransformation of chenodeoxycholic acid by Pseudomonas species NCIB 10590 under anaerobic conditions

The metabolism of chenodeoxycholic acid by Pseudomonas sp. NCIB 10590 under strict anaerobic conditions was studied. A range of unsaturated acidic and neutral metabolites were isolated and identified. The major acidic product was chola-4,6-dien-3-one-24-oic acid whilst the major neutral product was androsta-4,6-dien-3,17-dione. The major acidic products were 7 alpha-hydroxy-5 beta-cholan-3-oxo-24-oic acid, 3-oxo-4,6-pregnadien-20-carboxylic acid, 7 alpha-hydroxy-3-oxo-1,4-pregnadien-20-carboxylic acid, and 7 alpha-hydroxy-3-oxo-4-pregnen-20-carboxylic acid. The minor neutral products were androsta-1,4,6-trien-3,17-dione, 17 beta-hydroxyandrosta-4,6-dien-3,17-dione, 17 beta-hydroxyandrosta-1,4,6-trien-3-one, 7 alpha-hydroxyandrosta-1,4-dien-3,17-dione, and 7 alpha-hydroxyandrost-4-en-3,17-dione. In contrast to aerobic catabolism of chenodeoxycholic acid by Pseudomonas sp. NCIB 10590 in which 1,4-dienone steroids predominate, the major products described in this study are 4,6-dienone steroids. This is because of the induction of a 7 alpha-dehydroxylase enzyme under anaerobic conditions.