Cloning, purification, crystallization and preliminary crystallographic analysis of galactokinase from Pyrococcus furiosus.

Galactokinase catalyses the conversion of galactose to galactose-1-phosphate as the first step in the Leloir pathway, a metabolic route that eventually enables the degradation of galactose via the glycolytic pathway. Galactokinases have been isolated from a wide range of prokaryotic and eukaryotic organisms and the enzyme has been identified as a member of the GHMP kinase (galactokinase, homoserine kinase, mevalonate kinase and phosphomevalonate kinase) superfamily. Pyrococcus furiosus galactokinase was cloned, expressed in Escherichia coli, purified and crystallized using the hanging-drop method of vapour diffusion with ammonium sulfate as the precipitant.