Category: catabolism
Conversion of dietary galactose (primarily from lactose) into glucose-1-phosphate via the Leloir pathway. Galactose → galactose-1-P (galactokinase, GALK1) → glucose-1-P (galactose-1-P uridyltransferase, GALT — the Leloir enzyme; uses UDP-glucose as the UDP donor, regenerating UDP-galactose). Classic galactosemia = GALT deficiency: G1P accumulates, depletes phosphate + UDP, produces hepatic + renal + cerebral injury in the newborn period; lethal without lactose-free diet. Galactokinase deficiency = milder galactosemia variant with isolated cataracts. Epimerase deficiency = third variant. Newborn screening detects GALT specifically. Long-term outcomes (ovarian failure, learning difficulties) persist despite early diet correction.