Substrate specificity of alpha-L-arabinofuranosidase from plant scopolia japonica calluses and a suggestion with reference to the structure of beet araban.

Substrate specificity of alpha-L-arabinofuranosidase from plant Scopolia japonica was examined using three kinds of arabinodisaccharides prepared from natural sources of synthetically. This enzyme hydrolyzed arabinofuranosyl-arabinoses which had either an alpha-(1 leads to 3) or a alpha-(1 leads to 5) linkage, but hydrolyzed arabinopyranosyl-arabinose having a alpha-(1 leads to 5) linkage to a lesser degree. alpha-L-Arabinofuranosidase (alpha-L-arabinofuranoside arabinofuranohydrolase, EC 3.2.1.55), which was shown by us to be an exo-enzyme, degraded beet araban incompletely. Arabinose oligomers and galactose-containing fragments, isolated following acid hydrolysis of araban, were both incompletely degraded by the enzyme. The reasons for the incomplete degradation were explained by the novel finding of (1 leads to 2) linkages and arabinopyranosides and the inclusion of trace amounts of galactose into the carbohydrate chain of araban. This enzyme was practically non-reacting with the hydroxyprolyl-arabinose linkage of glycopeptides from plant cell walls.