Biosynthesis of coenzyme F430 in methanogenic bacteria. Identification of 15,17(3)-seco-F430-17(3)-acid as an intermediate.

Coenzyme F430 is a hydroporphinoid nickel complex present in all methanogenic bacteria. It is part of the enzyme system which catalyzes methane formation from methyl-coenzyme M. We describe here that under certain conditions a second nickel porphinoid accumulates in methanogenic bacteria. The compound was identified at 15,17(3)-seco-F430-17(3)-acid. The structural assignment rests on 14C-labelling experiments, fast-atom-bombardment mass spectra, 1H-NMR spectra of the corresponding hexamethyl ester, and ultraviolet/visible spectral comparison with model compounds. In cell extracts and in intact cells of methanogenic bacteria, 15,17(3)-seco-F430-17(3)-acid was converted to F430. These findings indicate that the new nickel-containing porphinoid is an intermediate in the biosynthesis of coenzyme F430.