ACT_3PGDH-like CD includes the C-terminal ACT (regulatory) domain of D-3-phosphoglycerate dehydrogenase (3PGDH)
ACT_3PGDH-like: The ACT_3PGDH-like CD includes the C-terminal ACT (regulatory) domain of D-3-phosphoglycerate dehydrogenase (3PGDH), with or without an extended C-terminal (xct) region found in various bacteria, archaea, fungi, and plants. 3PGDH is an enzyme that belongs to the D-isomer specific, 2-hydroxyacid dehydrogenase family and catalyzes the oxidation of D-3-phosphoglycerate to 3- phosphohydroxypyruvate, which is the first step in the biosynthesis of L-serine, using NAD+ as the oxidizing agent. In bacteria, 3PGDH is feedback controlled by the end product L-serine in an allosteric manner. In the Escherichia coli homotetrameric enzyme, the interface at adjacent ACT (regulatory) domains couples to create an extended beta-sheet. Each regulatory interface forms two serine-binding sites. The mechanism by which serine transmits inhibition to the active site is postulated to involve the tethering of the regulatory domains together to create a rigid quaternary structure with a solvent-exposed active site cleft. This CD also includes the C-terminal ACT domain of the L-serine dehydratase (LSD), iron-sulfur-dependent, beta subunit, found in various bacterial anaerobes such as Clostridium, Bacillus, and Treponema species. LSD enzymes catalyze the deamination of L-serine, producing pyruvate and ammonia. Unlike the eukaryotic L-serine dehydratase, which requires the pyridoxal-5'-phosphate (PLP) cofactor, the prokaryotic L-serine dehydratase contains an [4Fe-4S] cluster instead of a PLP active site. The LSD alpha and beta subunits of the 'clostridial' enzyme are encoded by the sdhA and sdhB genes. The single subunit bacterial homologs of L-serine dehydratase (LSD1, LSD2, TdcG) present in E. coli, and other Enterobacteriales, lack the ACT domain described here. Members of this CD belong to the superfamily of ACT regulatory domains.