nucleotide-binding domain (NBD) of Homo sapiens xylulose kinase (XK) and similar proteins
XK (EC 2.7.1.17), also called xylulokinase or D-xylulose kinase, catalyze the rate-limiting step in the ATP-dependent phosphorylation of D-xylulose to produce D-xylulose 5-phosphate (X5P), a molecule that may play an important role in the regulation of glucose metabolism and lipogenesis. The subfamily includes XKs mainly from eukaryote. They belong to the FGGY family of carbohydrate kinases, the monomers of which contain two large domains, which are separated by a deep cleft that forms the active site. This model includes both the N-terminal domain, which adopts a ribonuclease H-like fold, and the structurally related C-terminal domain.
Comment:catalytic residues (Asp, Thr, Asp) conserved in the FGGY family
Comment:Two Asp residues probably form a metal cofactor binding site and the second Asp residue acts as a catalytic base.
Comment:It has been proposed that the first Asp coordinates and positions the MgATP, and (in concert with the Mg2+) stabilizes the ADP leaving group during the phospho transfer. The second Asp would act as a general base during catalysis, assisting the removal of a proton from the attacking hydroxyl group. The Thr could stabilize the transition state.
Jiyao W et al.(2023). "The conserved domain database in 2023.",