A study on the galactosyltransferase activity of human gastric mucosa Part 1. Assay conditions with ovomucoid as a substrate.

The conditions assaying for UDP-galactosyltransferase in human gastric mucosa was studied. Ovomucoid without any pretreatment was employed as a substrate. The optimal pH was 6.8. Manganese, 2-mercaptoethanol and Triton X-100 were required for maximum enzyme activity. In the standard assay; 20 μl of enzyme solution was added to 30 μl of 50 mM MES buffer containing 5 mM 2-mercaptoethanol, 15 mM MnCl(2), 9.9mg protein/ml ovomucoid, 0.3 mM UDP-galactose, 1.7 μCi/ml UDP-[(3)H]-galactose and 1.5 mg/ml Triton X-100, and incubation was carried out at 37℃ for 20 min. [(3)H]-labelled ovomucoid was the only radioreactive reaction product detected. All galactose residue incorporated was liberated by β-galactosidase but not by α-galactosidase.