Molybdopterin adenine dinucleotide and molybdopterin hypoxanthine dinucleotide in formylmethanofuran dehydrogenase from Methanobacterium thermoautotrophicum (Marburg).

Formylmethanofuran dehydrogenase from Methanobacterium thermoautotrophicum was purified to apparent homogeneity and found to contain per mol (apparent molecular mass 110 kDa) 0.6 mol molybdenum, 4 mol non-heme iron, 4 mol acid-labile sulfur, and in addition, 0.7 mol of a pterin-containing co-factor (apparent molecular mass 800 Da) which has been characterized. The pterin material was extracted after alkylation by iodoacetamide and the extract subjected to HPLC on Lichrospher 100 RP-18. Three pterin compounds were resolved. On the basis of their UV/visible spectra and of the products formed after cleavage by nucleotide pyrophosphatase and alkaline phosphatase they were identified as the [di(carboxamidomethyl)]-derivatives of molybdopterin guanine dinucleotide (MGD), of molybdopterin adenine dinucleotide (MAD), and of molybdopterin hypoxanthine dinucleotide (MHD). The three pterin dinucleotides were present in the proportions 1:0.4:0.1.