The molybdenum cofactor of formylmethanofuran dehydrogenase from Methanosarcina barkeri is a molybdopterin guanine dinucleotide

Abstract The molybdenum cofactor of formylmethanofuran dehydrogenase from methanol-grown Methanosarcina barkeri was isolated as the [difcarboxami-domethyl)]-derivative. The alkylated factor showed an absorption spectrum and chemical properties identical to those recently reported for the molybdenum cofactor of dimethyl sulfoxide reductase from Rhodobacter sphaeroides . By treatment with nucleotide pyrophosphatase the factor was resolved into two components, which were identified as [di(carboxamidomethyl)]-molybdopterin and GMP by their absorption spectra, their retention times on Lichrospher RP-18, and by their conversion to dephospho-[di(carboxamidomcthyl)]-molybdopterin and guanosine. respectively, in the presence of alkaline phosphatase. The GMP-moiety was sensitive to pcriodate, identifying it as the 5'-isomer. These results demonstrate that the molybdenum cofactor isolated from formylmethanofuran dehydrogenase contains the phosphoric anhydride of molybdopterin and 5'-GMP.