Protein Domain : Hexokinase IPR001312

Type	Family
Description	Hexokinase ( ) [ , ] is an important glycolytic enzyme that catalyzesthe phosphorylation of keto- and aldohexoses (e.g. glucose, mannose and fructose) using MgATP as the phosphoryl donor.In vertebrates there are four major isoenzymes, commonly referred as types I, II, III and IV. Type IV hexokinase, which is often incorrectly designatedglucokinase [ ], is only expressed in liver and pancreatic beta-cells andplays an important role in modulating insulin secretion; it is a protein of a molecular mass of about 50 Kd. Hexokinases of types I to III, which have lowKm values for glucose, have a molecular mass of about 100 Kd. Structurally they consist of a very small N-terminal hydrophobic membrane-binding domainfollowed by two highly similar domains of 450 residues. The first domain has lost its catalytic activity and has evolved into a regulatory domain.In yeast there are three different isoenzymes: hexokinase PI (gene HXK1), PII (gene HXKB), and glucokinase (gene GLK1). All three proteins have a molecularmass of about 50 Kd.The hexokinase domain has an alpha/beta fold and is distinctly folded in two subdomains of unequal size: the large and small subdomains.The large subdomain comprises a six-stranded mixed β-sheet and a number of additional α-helices. On one side, the sheet packs against the smallsubdomain, and on the other side it is shielded by several α-helices. The dominant feature of the small subdomain is a five stranded mixed β-sheet.The sheet is flanked by two helices on one side and by one helix on the other. The subdomain also has an additional β-sheet formed by two antiparallelstrands [ , ].All these enzymes contain one (or two in the case of types I to III isozymes) strongly conserved region which has been shown [] to be involved in substrate binding.
Short Name	Hexokinase