In Vivo and In Vitro Evidence for N-Methylation as the Second Pathway-Specific Step in Ergoline Biosynthesis1

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Abstract
Experiments with precursors intramolecularly double-labeled with 15N and deuterium have shown that N-methyl-4-(γ, γ-dimethylallyl)tryptophan (Ib), but not its decarboxylation product, is an intact precursor of the tetracyclic ergoline elymoclavine (IIIb). An N-methyltransferase has been detected in cell-free extracts of Claviceps which catalyzes the transfer of the S-methyl group of S-adenosylmethionine to the amino group of 4-(γ, γ-dimethylallyl)tryptophan (Ia). These results strongly indicate that N-methylation of la is the second pathway-specific step in ergoline biosynthesis and they imply that pyridoxal phosphate cannot be involved as cofactor in the decarboxylation and C-ring closure steps in this biosynthesis.