Inactivation of alpha-Amylases from Thermoactinomyces vulgaris R-47, TVA I and TVA II, by [omega]- Epoxyalkyl alpha-D-Glucopyranoside

We found here that [omega]-epoxyalkyl alpha-D-glucopyranosides consisting of three, four and five alkyl carbons (alpha-E3G, alpha-E4G and alpha-E5G, respectively), which are known to be affinity-labeling reagents of beta -amylase, had the effect of inactivating two pullulan-hydrolyzing alpha-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, K sub(R), of alpha-E5G were calculated. The k/K sub(R) values of alpha-E5G for TVA I and TVA II were 13.1 x 10 super(-4) and 6.41 x 10 super(-4) M super(-1) . S super(-1) respectively. In terms of the power of inactivation, the orders for TVA I and TVA II were alpha-E5G>alpha-E3G[asymp]alpha-E4G, and alpha-E5G>alpha- E3G>alpha-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 beta -amylase and isomalto-dextranase.