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 antibi oticus, possess an intracellular glycosyltransferase capable of inacti vating oleandomycin by glysosylation of the 2'-hydroxyl group in the d esosamine moiety of the molecule [Vilches, C., Hernandez, C., Mendez, C. and Salas, J.A. (1992) J. Bacteriol. 174, 161-165]. Using a four-st ep purification procedure, we have purified an enzyme activity from th e culture supernatants from this organism which is able to release glu cose from the inactive glycosylated molecule thus reactivating the ant ibiotic activity. This enzyme activity appeared in the culture superna tants immediately before oleandomycin is detected. The enzyme (molecul ar mass 87 kDa) showed a high degree of substrate specificity, not act ing on other glycosylated macrolides such as methymycin, lankamycin an d rosaramicin which are substrates for the glycosyltransferase. A seco nd activity was detected corresponding to a 34-kDa polypeptide which p robably originates from proteolytic cleavage of the larger polypeptide . The 87-kDa polypeptide possibly catalyses the last biosynthetic step in oleandomycin biosynthesis by S. antibioticus.