Galactokinase catalyses the first reaction in the galactose metabolism pathway, the ATP-dependent phosphorylation of galactose, yielding galactose-1-phosphate [<cite idref="PUB00003653"/>, <cite idref="PUB00004765"/>].Deficiency in this enzyme results in the disease galactosemia, which is responsible for theformation of cataracts in newborn babies, and is possibly responsible for presenile cataracts inadults [<cite idref="PUB00004765"/>]. In yeast, the GAL3 gene product is required for the GAL4-mediated inductionof other enzymes involved in galactose metabolism. The induction of GAL1 production then reinforcesthis process, increasing the expression of other galactose-inducible genes. GAL3 has been shown tobe similar to the GAL1 protein [<cite idref="PUB00003653"/>].<p>This entry represents a conserved signature pattern located in the N-terminal domain of galactokinases.</p>