Cloning of the galactokinase cDNA and identification of mutations in two families with cataracts.

Galactokinase is an essential enzyme for the metabolism of galactose and its deficiency causes congenital cataracts during infancy and presenile cataracts in the adult population. We have cloned the human galactokinase cDNA, which maps to chromosome 17q24, and show that the isolated cDNA expresses galactokinase activity in bacteria and mammalian cells. We also describe two different mutations in this gene in unrelated families with galactokinase deficiency and cataracts. The availability of the cloned galactokinase gene provides an important reference to identify mutations in patients with galactokinase deficiency and cataracts.