Abstract
Cycloalkyl β-D-glucopyranosides were synthesized by transglucosylation of a β-glucosidase from fungi. When cyclopropanemethanol (CPAM), cyclopentanol (CPE) and cyclopentanemethanol (CPEM) were used as the acceptors, the enzyme stereoselectively synthesized cyclopropylmethyl, cyclopentyl and cyclopentylmethyl β-D-glucopyranosides (abbreviated to CPAM-β-G, CPE-β-G and CPEM-β-G, respectively) from cellobiose as a glucosyl donor. Among the above three β-glucopyranosides, only CPEM-β-G was found to inhibit sweet almond enzyme activity (Ki=0.15± 0.02 mM). Other cycloalkyl β-D-glucopyranosides had little/or no inhibitory activity toward the β-glucosidases examined. CPEM itself had a weak inhibitory activity for sweet almond enzyme, with an uncompetitive type. However, the introduction of a glucose molecule to CPEM as a glycon converted its inhibition type into a competitive one. The Ki value of CPEM-β-G for the enzyme was reduced to about 1/7 compared with the corresponding cyclic alcohol. As it is expected that CPEM-β-G is much more likely to inhibit the activity of an enzyme from plant origin compared with those from fungi, we studied the possibility of CPEM-β-G inhibiting the activities of β-glucosidases extracted from the cut flowers on the basis of their kinetic data.
