N-furfurylformamide as a pseudo-substrate for formylmethanofuran converting enzymes from methanogenic bacteria

Methanofuran (4-[N-(4,5,7-tricarboxyheptanoyl-gamma-L-glutamyl)-gamma-L- glutamyl)-p-(beta-aminoethyl)phenoxymethyl]-2-(aminomethyl)furan is a coenzyme involved in methanogenesis. The N-formyl derivative is an intermediate in the reduction of CO2 to CH4 and the disproportionation of methanol to CO2 and CH4. Formylmethanofuran dehydrogenase and formylmethanofuran:tetrahydromethanopterin formyltransferase are the enzymes catalyzing its conversions. We report here that the two enzymes from Methanosarcina barkeri and the formyltransferase from Methanobacterium thermoautotrophicum can also use N-furfurylformamide as a pseudo-substrate albeit with higher apparent Km and lower apparent Vmax values. N-Methylformamide, formamide, and formate were not converted indicating that the furfurylamine moiety of methanofuran is the minimum structure required for the correct binding of the coenzyme.