Pyrimidine (PYR) binding domain of pyruvate ferredoxin oxidoreductase (PFOR), indolepyruvate ferredoxin oxidoreductase alpha subunit (IOR-alpha), and related proteins.
Thiamine pyrophosphate (TPP family), pyrimidine (PYR) binding domain, of pyruvate ferredoxin oxidoreductase (PFOR), indolepyruvate ferredoxin oxidoreductase (IOR) alpha subunit (IOR-alpha), and related proteins, subfamily. The PYR domain is found in many key metabolic enzymes which use TPP (also known as thiamine diphosphate) as a cofactor. TPP binds in the cleft formed by a PYR domain and a PP domain. The PYR domain, binds the aminopyrimidine ring of TPP, the PP domain binds the diphosphate residue. A polar interaction between the conserved glutamate of the PYR domain and the N1' of the TPP aminopyrimidine ring is shared by most TPP-dependent enzymes, and participates in the activation of TPP. The PYR and PP domains have a common fold, but do not share strong sequence conservation. The PP domain is not included in this sub-family. Most TPP-dependent enzymes have the PYR and PP domains on the same subunit although these domains can be alternatively arranged in the primary structure. TPP-dependent enzymes are multisubunit proteins, the smallest catalytic unit being a dimer-of-active sites. For many of these enzymes the active sites lie between PP and PYR domains on different subunits. However, for the homodimeric enzyme Desulfovibrio africanus pyruvate:ferredoxin oxidoreductase (PFOR), each active site lies at the interface of the PYR and PP domains from the same subunit. This subfamily includes proteins characterized as pyruvate NADP+ oxidoreductase (PNO). PFOR and PNO catalyze the oxidative decarboxylation of pyruvate to form acetyl-CoA, a crucial step in many metabolic pathways. The facultative anaerobic mitochondrion of the photosynthetic protist Euglena gracilis oxidizes pyruvate with PNO. IOR catalyzes the oxidative decarboxylation of arylpyruvates, such as indolepyruvate or phenylpyruvate.