Pyrimidine (PYR) binding domain of pyruvate decarboxylase (PDC), indolepyruvate decarboxylase (IPDC) and related proteins.
Thiamine pyrophosphate (TPP family), pyrimidine (PYR) binding domain of pyruvate decarboxylase (PDC) and indolepyruvate decarboxylase (IPDC) 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. 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 the active sites lie between PP and PYR domains on different subunits. PDC catalyzes the conversion of pyruvate to acetaldehyde and CO2 in alcoholic fermentation. IPDC plays a role in the indole-3-pyruvic acid (IPA) pathway in plants and various plant-associated bacteria, it catalyzes the decarboxylation of IPA to IAA. Also belonging to this group is Mycobacterium tuberculosis alpha-keto acid decarboxylase (MtKDC) which participates in amino acid degradation via the Ehrlich pathway, and Lactococcus lactis branched-chain keto acid decarboxylase (KdcA) an enzyme identified as being involved in cheese ripening, which exhibits a very broad substrate range in the decarboxylation and carboligation reactions.