β-アミラーゼの触媒部位とアフィニティラベル

抄録

The affinity labeling of a functional carboxyl group in the active site of B-amylase is described. 2, 3-Epoxypropyl α-D-glucopyranoside (α-EPG) is a specific irreversible inactivator for β-amylases (soybean, sweet potato, barley, and Bacillus cereus), and the binding of α-EPG is stoichiometric, i, e., one α-EPG molecule per an active site of enzyme, α-EPG acts as an affinity labeling reagent and a mechanism-based inactivator for soybean p-amylase . It is demonstrated that the carboxylate of Glu 186 affinity-labeled by α-EPG is a functional group (pKa3.5) at the catalytic site of soybean β-amylase. The amino acid sequence around the Glu 186 is well conserved among all of the five β-amylases with known sequences.