Abstract
We found here that ω-epoxyalkyl α-D-glucopyranosides consisting of three, four and five alkyl carbons (α-E3G, α-E4G and α-E5G, respectively), which are known to be affinity-labeling reagents of β-amylase, had the effect of inactivating two pullulan-hydrolyzing α-amylases from Thermoactinomyces vulgaris R-47, TVA I and TVA II, at high concentration (ca. 0.1-1.5 M). The inactivation exhibited saturation kinetics of a two-step mechanism, and an inactivation rate constant, k, and equilibrium dissociation constant, KR, of α-E5G were calculated. The k/KR values of α-E5G for TVA I and TVA II were 13.1 × 10-4 and 6.41 × 10-4 M-1 · S-1 respectively. In terms of the power of inactivation, the orders for TVA I and TVA II were α-E5G>α-E3G≈α-E4G, and α-E5G>α-E3G>α-E4G, respectively. The findings indicated that the relation between the lengths of the alkyl carbons and the inactivation of TVA I and TVA II differs from that for β-amylase and isomalto-dextranase.
