Chemistry of bleomycin. XXVI. Biosynthetic study using 13C-enriched precursors.

3-Morpholinopropylamino-bleomycin (MOP-BLM) was produced by the culture of Streptomyces verticillus ATCC 15003 grown in the presence of a 13C-enriched compound and 3-morpholinopropylamine in the medium, and the resulting MOP-BLM was analyzed by 13C-NMR spectrometry. In the spectrum of MOP-BLM produced by addition of 13C-methyl-L-methionine, the intensities of two signals assigned to the methyl carbon of the pyrimidine chromophore and of the 2-position of the 4-amino-3-hydroxy-2-methylpentanoic acid moiety were remarkably enhanced. When DL-alanine-3-13C was added, the signals emanated from the 5-methyl and 2-methine carbons of the 4-amino-3-hydroxy-2-methylpentanoic acid moiety were markedly enhanced. These results definitely indicate that the methyl group of the pyrimidine moiety originates from methionine-methyl group and the carbon skeleton of the pentanoic acid moiety is formed from alanine, acetate and methionine-methyl group. This study also revealed that the former assignment of the two signals from the two methyl carbons of the 4-amino-3-hydroxy-2-methylpentanoic acid moiety must be reversed.