Purification and characterization of an extracellular enzyme from Streptomyces antibioticus that converts inactive glycosylated oleandomycin into the active antibiotic

Cell‐free extracts from the oleandomycin producer, Streptomyces antibioticus, possess an intracellular glycosyltransferase capable of inactivating oleandomycin by glysosylation of the 2′‐hydroxyl group in the desosamine moiety of the molecule [Vilches, C., Hernández, C., Méndez, C. & Salas, J. A. (1992) J. Bacteriol. 174, 161–165]. Using a four‐step purification procedure, we have purified an enzyme activity from the culture supernatants from this organism which is able to release glucose from the inactive glycosylated molecule thus reactivating the antibiotic activity. This enzyme activity appeared in the culture supernatants immediately before oleandomycin is detected. The enzyme (molecular mass 87 kDa) showed a high degree of substrate specificity, not acting on other glycosylated macrolides such as methymycin, lankamycin and rosaramicin which are substrates for the glycosyltransferase. A second activity was detected corresponding to a 34‐kDa polypeptide which probably originates from proteolytic cleavage of the larger polypeptide. The 87‐kDa polypeptide possibly catalyses the last biosynthetic step in oleandomycin biosynthesis by S. antibioticus.