Hydrolysis of some natural and synthetic bile acid conjugates by Cercospora melonis.

Analogs of natural bile acid conjugates were incubated with both whole-cell cultures and cell-free extracts of the fungus Cercospora melonis CBS 162.60. Those conjugates containing both an alpha-amino group and a carboxylic acid group in the amino acid moiety were the most susceptible to hydrolysis. Substitution with a beta-amino group and (or) a sulfonic acid group greatly reduced the extent of hydrolysis. With all conjugates tested, significant losses of total bile acid were observed on incubation with whole-cell cultures. Two factors have been implicated as contributing to these losses. First, bile acids may be degraded to nonsteroidal products by an inducible enzyme system. Second, bile acids may be bound to mycelia in a manner not reversed by the extraction technique.