Effects of glucose, ethanol, Hg(II) and Cu(II) on almond beta-glucosidase.

The kinetic parameters of almond beta-glucosidase (beta-D-glucoside glucohydrolase; EC 3.2.1.21), using pNGP as substrate were kM = 2.24 +/- 0.11 mM and Vmax 588 +/- 25.1 U/mg protein. Only Hg(II) and Cu(II) showed irreversible inactivation of the enzyme. However, when these metals were present in the reaction system the inhibition effects were consistent with a mixed-type inhibition pattern (Cu(II) ki: 5.08 mM and Hg(II) ki: 0.07 mM). The glucose kinetic effect was also consistent with a mixed-type inhibition (ki = 406 mM) pattern with pNGP as varied substrate. Ethanol displayed the kinetic pattern of competitive inhibition (ki = 640 mM).