NADP binding domain of methylene tetrahydromethanopterin dehydrogenase
Methylene Tetrahydromethanopterin Dehydrogenase (H4MPT DH) NADP binding domain. NADP-dependent H4MPT DH catalyzes the dehydrogenation of methylene- H4MPT and methylene-tetrahydrofolate (H4F) with NADP+ as cofactor. H4F and H4MPT are both cofactors that carry the one-carbon units between the formyl and methyl oxidation level. H4F and H4MPT are structurally analogous to each other with respect to the pterin moiety, but each has distinct side chain. H4MPT is present only in anaerobic methanogenic archaea and aerobic methylotrophic proteobacteria. H4MPT seems to have evolved independently from H4F and functions as a distinct carrier in C1 metabolism. Amino acid DH-like NAD(P)-binding domains are members of the Rossmann fold superfamily and include glutamate, leucine, and phenylalanine DHs, methylene tetrahydrofolate DH, methylene-tetrahydromethanopterin DH, methylene-tetrahydropholate DH/cyclohydrolase, Shikimate DH-like proteins, malate oxidoreductases, and glutamyl tRNA reductase. Amino acid DHs catalyze the deamination of amino acids to keto acids with NAD(P)+ as a cofactor. The NAD(P)-binding Rossmann fold superfamily includes a wide variety of protein families including NAD(P)- binding domains of alcohol DHs, tyrosine-dependent oxidoreductases, glyceraldehyde-3-phosphate DH, lactate/malate DHs, formate/glycerate DHs, siroheme synthases, 6-phosphogluconate DH, amino acid DHs, repressor rex, NAD-binding potassium channel domain, CoA-binding, and ornithine cyclodeaminase-like domains. These domains have an alpha-beta-alpha configuration. NAD binding involves numerous hydrogen and van der Waals contacts.
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