A simple assay for uridine diphosphate galactose 4-epimerase activity.

A simple fluorescent test for the activity of blood uridine diphosphate galactose 4-epimerase which converts uridine diphosphate galactose to uridine diphosphate glucose is described. The enzyme activity is visually estimated by to reduction of NAD+ (non fluorescent) to NADH (fluorescent) in a coupled reaction with uridine diphosphate glucose dehydrogenase. The appearance of fluorescence indicates that epimerase activity is present in the sample. The usefulness of this test in newborn screening programs for inborn errors of galactose metabolism is stressed.