In most organisms, the conversion of Galactose to the more metabolically useful Glucose-1-Phosphate is accomplished by the action of four enzymes that constitute the Leloir pathway. In the first step of this pathway, Beta-D-Galactose is epimerized to Alpha-D-Galactose by GALM (Galactose Mutarotase/Aldose 1-Epimerase) (Ref.1). The active site of GALM is positioned in a rather open cleft with the hydroxyl groups of Galactose lying within hydrogen bonding distance to a number of side chains, the reaction catalyzed by human GALM proceeds via Glu-307 (Glutamic acid-307) and His-176 (Histidine-176). Till now no diseases have been attributed to mutations in human GALM. The next step involves the ATP-dependent phosphorylation of Alpha-D-Galactose by GalK (Galactokinase) to yield Galactose-1-Phosphate. Deficiencies in this enzyme lead to [...]