Thiamine pyrophosphate (TPP family), PFOR_PNO subfamily, TPP-binding module; composed of proteins similar to the single subunit pyruvate ferredoxin oxidoreductase (PFOR) of Desulfovibrio Africanus, present in bacteria and amitochondriate eukaryotes. This subfamily also includes proteins characterized as pyruvate NADP+ oxidoreductase (PNO). These enzymes are dependent on TPP and a divalent metal cation as cofactors. PFOR and PNO catalyze the oxidative decarboxylation of pyruvate to form acetyl-CoA, a crucial step in many metabolic pathways. Archaea, anaerobic bacteria and eukaryotes that lack mitochondria (and therefore pyruvate dehydrogenase) use PFOR to oxidatively decarboxylate pyruvate, with ferredoxin or flavodoxin as the electron acceptor. The PFOR from cyanobacterium Anabaena (NifJ) is required for the transfer of electrons from pyruvate to flavodoxin, which reduces nitrogenase. The facultative anaerobic mitochondrion of the photosynthetic protist Euglena gracilis oxidizes pyruvate with PNO.
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