PARTIAL-PURIFICATION AND CHARACTERIZATION OF A HYDROXAMIC ACID GLUCOSIDE BETA-D-GLUCOSIDASE FROM MAIZE

Beta-Glucosidase activities measured in extracts from maize leaves during development gave different curves when p-nitrophenyl beta-D-glucopyranoside (PNP-Glc) or hydroxamic acid glucoside (Hx-Glc) were the substrates. The PNP-Glc glucosidase had a M(r) of 60 000 and an isoelectric point of 6.4, whereas the Hx-Glc glucosidase had a M(r) of 158000 and an isoelectric point of 4.8. This latter enzyme had an optimum pH of activity at 6.0, was inhibited by castanospermine and, when partially purified, accepted PNP-Glc as well as Hx-Glc as substrates, albeit with a lower activity for the former.