Characterization, Hydrolytic Activity and Variations throughout Growth of a Cell Wall β-Glucosidase and a-Galactosidase from Cicer arietinum epicotyls

Abstract

Summary In the cell walls of epicotyls of Cicer arietinum we found β-glucosidase and α-galactosidase activities, the former being predominant. We purified and characterized these enzymatic activities. The β-glucosidase activity is found associated with a protein fraction that also shows β-galactosidase and β-xylosidase activity. It is formed by two subunits of approximately 60-65 kDa, with elevated activity between pH 6 and 8 and an optimal temperature of 70 °C, inhibited by Hg 2+ . The values of K m and V max vary for each of its principal activities, being 2.2 mM and 378.6 nkat (mg protein) -1 , respectively, for βglucosidase activity. The fraction with the a-galactosidase activity is also formed by subunits of molecular weight of 35-45 kDa. It shows an optimum pH of 5 and 40 °C, its K m and V max being 0.27 mM and 32.8 nkat (mg protein) -1 . It is inhibited by Hg 2+ and galactose. Throughout growth of the epicotyls, β-glucosidase activity increased and α-galactosidase showed an activity profile with a maximum to the 5th day. These enzymes were not able to hydrolyze the non-cellulosic fractions of the cell wall. Its physiological role remains unknown.