Hexokinase Domain Containing Protein 1 (HKDC1)

Hexokinases (HK) phosphorylate sugar immediately upon its entry into cells allowing these sugars to be metabolized. A total of four hexokinases have been characterized in a diversity of vertebrates—HKI, HKII, HKIII, and HKIV. HKIV is often called glucokinase (GCK) and has half the molecular weight of the other hexokinases, as it only has one hexokinase domain, while other vertebrate HKs have two.

A fifth hexokinase-like gene, HKDC1 that exists and is expressed in diverse vertebrates. Analysis of the amino acid sequence of HKDC1 suggests that it may function as a hexokinase. GCK evolved from a two hexokinase domain-containing gene, but has lost its N-terminal hexokinase domain. Parallel changes in enzymatic function of HKI and HKIII have occurred.