Purification and Characterization of a ß-Glucosidase Specific for 2,4-Dihydroxy- 7-methoxy-l,4-benzoxazin-3-one (DIMBOA) Glucoside in Maize

Akira Oikawa, Kenkichi Ebisui, Masayuki Sue, Atsushi Ishihara and Hajime Iwamura Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan, and CREST, Japan Science and Technology Corporation (JST) Z. Naturforsch. 54c, 181-185 (1999); received November 19, 1998/January 11, 1999 Benzoxazinones, Zea mays, Gramineae, ß-Glucosidase Occurrence and properties of hydroxamic acid glucoside glucosidase were investigated in 10-day-old, autotrophic maize (Zea mays L.) in which 2,4-dihydroxy-7-methoxy-l,4benzoxazin-3-one glucoside (DIMBOA-G) is a major benzoxazinone component. Crude ex­ tracts of both leaves and roots showed glucosidase activity for both DIMBOA-G and 2,4dihydroxy-l,4-benzoxazin-3-one glucoside (DIBOA-G). A cation-exchange chromatography after cryoprecipitation of the extract from leaves gave a peak with both activities, and further purification by ion-exchange and hydroxyapatite chromatography gave a fraction with an apparent homogeneity, the purification being 560 fold. The Km values (m M ) of the purified glucosidase were 0.16 for DIMBOA-G, 0.68 for DIBOA-G and 2.96 for p-nitrophenyl-ß-Dglucopyranoside. The activity on salicin and esculin was too low to be detected. The data indicate that a glucosidase specific for DIMBOA-G comes into contact with constitutive benzoxazinone glucosides producing defensive aglycone when plants are damaged by micro­ bial or insect attacks.