CHARACTERIZATION OF BETA-GALACTOSIDASE ISOZYMES OF RIPENING PEPPERS

Activity of beta-galactosidase (EC 3.2.1.23) and isozymes of the New M exican type pepper were assayed in ripening fruit and characterised in order to further understand the possible role this enzyme plays in fr uit ripening. Total beta-galactosidase activity increased in New Mexic an type peppers (NM chile) as they ripened. To a lesser extent, xylosi dase and beta-glucosidase increased from the mature green stage to the turning stage of ripening and then decreased in the red ripe stage. C ation exchange chromatography indicated two prominent beta-galactosida se peaks depending on stage of ripeness. In mature NM green chile, one large anionic, and in NM red chile, one large cationic peak was found . Isoelectric focusing-polyacrylamide gel electrophoresis (IEF-PAGE) s eparated one isozyme from mature green NM chile (pI 4.6) and an additi onal beta-galactosidase isozyme as NM chile turned from green to red ( pI 8.0). The cationic beta-galactosidase isozyme from red NM chile ext ract had an apparent native-molecular weight of 51 kDa. The optimum pH for beta-galactosidase activity in both red and green NM chile was be tween 3 and 4.5. Stable enzyme activity was observed from 25 to 50 deg rees C. beta-Galactosidase from red NM chile had a K-m of 0.87 mM and V-max of 12.3 nKat, while the values for green NM chile beta-galactosi dase were 2.5 mM and 8.3 nKat. The heavy metal ions Ag2+ and Hg2+ inhi bited beta-galactosidase activity by 100% and 90%, respectively.