The proposed research seeks to establish the mechanism by which UDP-galactose-4-epimerase catalyzes non-stereospecific hydrogen transfer between substrates and bond pyridine nucleotide via UDP-4-ketosugar intermediates. It is proposed to study the chemical and physical interactions between this enzyme and UDP-glucose analogs and pyridine nucleotide analogs. It is also proposed to study the mechanistic relationships between electron transfer and group transfer in reactions catalyzed by alpha-ketoacid dehydrogenase complexes.