nucleotide-binding domain (NBD) of hexokinase isozymes PI and PII from fungal hexokinase (HK) domain family
Hexokinase (EC 2.7.1.1) possesses the ability to transfer an inorganic phosphate group from ATP to a substrate. It catalyzes the ATP-dependent phosphorylation of aldo- and keto-hexose sugars to the hexose-6-phosphate (H6P). It can catalyze this reaction on glucose, fructose, sorbitol and glucosamine, and as such is the first step in a number of metabolic pathways. Hexokinase contains two structurally similar domains. Some members of the family have two copies of each of these domains. There are three isozymes of hexokinase in yeast (PI, PII and glucokinase): isozymes PI and PII phosphorylate both aldo- and keto-sugars; glucokinase (EC 2.7.1.2) is specific for aldo-hexoses. Early meiotic induction protein 2 (EMI2, also known as glucokinase-2, EC 2.7.1.2) might be another isozyme of hexokinase in yeast. Yeast hexokinases reveal a well-defined catalytic pocket that binds ATP and hexose, allowing easy transfer of the phosphate from ATP to the sugar. The family corresponds to hexokinase PI and PII, which are also known as hexokinase-1/hexokinase-A and hexokinase-2/hexokinase-B, respectively.
Feature 1: catalytic site [active site], 3 residue positions
Conserved feature residue pattern:D T D
Evidence:
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.",