Galactose-1-phosphate in the pathophysiology of galactosemia.

In galactosemia, galactose-1-phosphate (gal-1-P) is not properly metabolized and accumulates in the fetus and after birth in various tissues when lactose or galactose is ingested. Well-treated galactosemics retain a low level of red cell gal-1-P which increases after breaks of diet. The ester is an indicator of the biogenesis of galactose from glucose and has been considered a pathogenic agent by inhibiting enzymes such as glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, phosphoglucomutase, and glycogen phosphorylase, but the evidence remains presumptive. A futile cycle of galactose phosphorylation and dephosphorylation, and the sequestration of phosphorus in gal-1-P are also suspected to play a role in the pathogenesis of galactosemia.