C-terminal ACT (regulatory) domain of D-3-phosphoglycerate dehydrogenase (3PGDH)
The C-terminal ACT (regulatory) domain of D-3-phosphoglycerate dehydrogenase (3PGDH), with an extended C-terminal (xct) region from 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. Some 3PGDH enzymes have an additional domain formed by an extended C-terminal region. This additional domain introduces significant asymmetry to the homotetramer. Adjacent ACT (regulatory) domains interact, creating two serine-binding sites, however, this asymmetric arrangement results in the formation of two different and distinct domain interfaces between identical domains in the asymmetric unit. How this asymmetry influences the mechanism of effector inhibition is still unknown. Members of this CD belong to the superfamily of ACT regulatory domains.