Microbial transformation of azacarbazoles. V. Studies on N-1 methylation of 4-methyl-alpha-carboline by Kitasatosporia setae strain

N-1 methylation of an azacarbazole, 4-methyl-alpha-carboline by Kitasatosporia setae was associated with antifungal metabolite production. Incubation of 4-methyl-alpha-carboline with intact cells or homogenates of Kitasatosporia setae and L-/14CH3/-methionine or adenosyl-S-/14CH3/-L-methionine yielded radioactive products, 1,4-dimethyl-alpha-iso-carboline. The presence of 14C-labelled methyl groups in antifungal metabolite has been also observed. Mutants of Kitasatosporia setae with lost abilities to produce antifungal metabolite did not convert 4-methyl-alpha-carboline into its methyl derivative.