Identification and characterization of a new intermediate in the ribosylative inactivation pathway of rifampin by Mycobacterium smegmatis

Mycobacterium smegmatis DSM 43756 inactivates rifampin by ribosylation. To study this process of rifampicin, all possible inactivated forms of the ant ibiotic were extracted and purified. Structural studies showed the presence of a new inactivation product, designated RIP-TAp(23-phosphoribosyl-rifamp in), Formation of 23(O-ADP-ribosyl)rifampin (RIP-TAs) is the first step, fo llowed by removal of AMP to give rise to the newly identified compound. Las tly, dephosphorylation leads to formation of 23-ribosyl-rifampin (RIP-Mb), Feeding experiments with the ADP-ribosylated antibiotic obtained from the c ell homogenates of an Escherichia coli strain carrying the cloned M. smegma tis gene confirmed this rifampin inactivation process.