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.
Comment:The bound serine inhibitor spans the ACT-ACT interface forming hydrogen bond with conserved residues (generally His and Asn) of one subunit with a second Asn of the adjacent subunit.
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