Abstract
Riboflavin-β-galactoside was isolated in crystalline form from the incubation mixture containing o-nitrophenyl-β-D-galactopyranoside (o-NPGa), riboflavin, and crystalline β-galactosidase from Escherichia coli, and identified as 5'-D-riboflavin-β-D-galactopyranoside. Galactosides of several riboflavin analogues, such as dichloroflavin, D-araboflavin and 6,7-dimethyl-ribolumazine, were synthesized by β-galactosidase. Moreover, it was found that sugar alcohols, pyridoxine and nucleosides were able to act as the acceptor of β-D-galactosyl residue of o-NPGa. O-β-D-Ga1actosy1-5-ribitol was isolated as powdered preparations by application of paper chromatographic procedures from the incubation mixture containing o-NPGa, ribitol and crystalline β-galactosidase, and identified from its R_F value, production of ribitol and galactose after the hydrolysis by acid or β-galactosidase, and oxidation with sodium metaperiodate. From these results, it is considered that galactosyl transfer reaction to riboflavin and its analogues is functioned by β-ga1actosidase.
