Galactokinase Deficiency

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Galactosemia type II; Galk deficiency

Definition and Characteristics

Autosomal recessive inborn error in galactose metabolism leading to hypergalactosemia and cataract formation.


Overall estimates of homozygotes range from 1:100,000 to 1:1,000,000. Some mutations, however, have higher frequencies in particular populations such as the A198V mutation in Japanese, Korean and Chinese populations [1] and the P28T mutation in Roma and Bosnian populations [2,3].


GALK1 coding for galactokinase, localized on chromosome 17q24 [4].

Molecular and Systemic Pathophysiology

Galactokinase functions in normal galactose metabolism by catalyzing the MgATP-dependent phosphorylation of the C-1 hydroxyl group of α-d-galactose. Approximately 25 mutations (including base substitutions, base deletions, and larger deletions) have been reported in human galactokinase, which give rise to Type II galactosemi