AN ENDOGLYCOSIDASE FROM GRAPE BERRY SKIN OF CV M. ALEXANDRIA HYDROLYZING POTENTIALLY AROMATIC DISACCHARIDE GLYCOSIDES

We present evidence on the presence of an endoglycosidase in grape ski ns able to split the heterosidic linkage of disaccharide glycosides, r eleasing disaccharide and aglycon. Its extraction from grape skins (cv . Muscat of Alexandria) was possible with the use of a detergent (poly (ethylene glycol)). The enzyme was purified about 1000-fold successive ly by chromatography on DEAE Sepharose CL 6B, CM 20 Poros, and Protein -Pak SW 300. The optimum pH and temperature activity were found to be similar to levels reported for other plant glycosidases. K-m and V-max values for pNP-beta-rutinoside were 1.69 mM and 275 nkat/mg, respecti vely, with a molecular mass of 58 000. The enzyme was quite tolerant t o glucose inhibition (K-i = 212 mM). Hydrolysis of monoterpenyl and 2- phenylethyl glycosides (arabinofuranosyl-, rhamnopyranosyl-, apiofuran osylglucosides) from grape and arabinopyranosyl- and xylopyranosylgluc osides from other plants yielded the corresponding disaccharides and a glycons. The identity of the released sugars was confirmed by GC-EIMS/ GC-NCIMS analysis of trifluoroacetylated derivatives.