BIOSYNTHESIS OF BLASTICIDIN-S - CELL-FREE DEMONSTRATION OF N-METHYLATION AS THE LAST STEP

In continuing studies on the biosynthesis of the antifungal antibiotic blasticidin S, 1, a crude cell-free extract was prepared from Streptomyces griseochromogenes that converted demethylblasticidin S and S-adenosyl-L-[(CH3)-C-14]methionine to 1a. Hydrolysis of 1a to blastidic acid (delta-N-methyl-L-beta-arginine) and cytosinine and radiochemical analysis of the products confirmed that the former contained all the C-14 radioactivity. Thus, N-methylation is the last step in the biosynthesis of 1.