Specificity of a particulate glucosyltransferase in seedlings of Pisum sativum L. which catalyzes the formation of 5'-O-(.BETA.-D-glucopyranosyl)pyridoxine.

Abstract

A glucosyltransferase, catalyzing the transfer of D-glucose from UDP-glucose to the 5''-hydroxyl group of pyridoxine, was isolated as a particulate enzyme from seedlings of podded pea (P. sativum L. cv. Kinusaya). The enzyme required additional Mg2+ for its function. The pH optimum for glucosylation of pyridoxine was between 7.8 and 8.8. The enzyme showed high specificity for UDP-glucose and relative specificity for glucosyl acceptor: pyridoxine was replaceable by pyridoxamine. Several compounds tested other than vitamin B6 failed to serve as the acceptor. A methylene group on C-4 participated in the formation of enzyme-substrate complex and the rate of glucosylation was dependent upon the C-4 substituent. From the results of kinetic studies and an experiment in vivo, the enzyme was inferred to be UDP-glucose: pyridoxine 5''-O-.beta.-glucosyltransferase.