Bile acid transformations by Alcaligenes recti

Article abstract of DOI:10.1016/0039-128X(93)90057-T

Metabolism of cholic acid, chenodeoxycholic acid, ursodeoxycholic acid, and deoxycholic acid by the grown cells of the bacterium Alcaligenes recti suspended in water was studied.Each isolated metabolite was characterized by the application of various spectroscopic methods.Cholic acid, chenodeoxycholic acid, ursodeoxycholic acid, and deoxycholic acid yielded methylated derivatives 3α-methoxy-7α,12α-dihydroxy-5β-cholanoic acid, 3α-methoxy-7α-hydroxy-5β-cholanoic acid, 3α-methoxy-7β-hydroxy-5β-cholanoic acid, and 3α-methoxy-12α-hydroxy-5β-cholanoic acid, respectively.In addition, cholic acid furnished 7α,12α-dihydroxy-3-oxochol-4-en-24-oic acid; chenodeoxycholic acid gave 7α-hydroxy-3-oxo-5β-cholanoic acid and 7α-hydroxy-3-oxochol-4-en-24-oic acid while ursodeoxycholic acid yielded 7β-hydroxy-3-oxochol-4-en-24-oic acid and 3-oxochola-4,6-dien-24-oic acid.The formation of various metabolites showed that two competitive enzymic reactions, i.e., selective methylation of the 3α-hydroxy group and dehydrogenation in the A/B rings, were operative.The methylation process was found to be enzymic involving an S-adenosyl-L-methionine (AdoMet)-dependent methyl transferase, and this reaction appeared to be inhibitory to the process of degradation of the ring system.In the other reaction sequence, degradation of the ring system was initiated by dehydrogenation of the 3α-hydroxy group.A 7β-dehydratase activity producing the Δ⁶ double bond was also noticeable in the metabolism of ursodeoxycholic acid. Keywords: sterols; bile acids; metabolites; microbial transformation; Alcaligenes recti; bacterial transformation