Cyclic hydroxamic acids and a glucosidase that occur in I ye seedlings were
investigated. The concentration of the glucoside of 2.3-dihydroxy-1,4-benz
oxazin-3-one (DIBOA-Glc) in shoots increased soon after germination and dec
reased to a lower, constant level as the plants started autotrophic growth.
Cyclic hydroxamic acid glucoside beta-glucosidase activity also occurred t
ransiently, and the timing of the increase and decrease was concurrent with
that of cyclic hydroxamic acid glucosides. The glucosidase was isolated fr
om 48-h-old rye shoots and purified to apparent homogeneity by using isoele
ctric precipitation, anion exchange chromatography, and gel filtration. The
isoelectric point and the optimum reaction temperature were 4.9-5.1 and 25
-30 degrees C, respectively. The N-terminal amino acid sequence was almost
identical to that of the wheat glucosidases, but did not show any similarit
y to the sequences of other glucosidases of plant origin. SDS- and native-P
AGE analyses showed that rye had several isozymes of glucosidase, and each
isozyme was an oligomer of 60-kDa monomers with a molecular mass of similar
to 300 kDa. The enzyme was highly active not only for DIMBOA-Glc but also
for its 7-demethoxy analogue. DIBOA-Glc, which was different from the speci
ficities of maize and wheat glucosidases. (C) 2000 Elsevier Science Ireland
Ltd. All rights reserved.