An .ALPHA.-amylase inhibitor from cranberry bean (Phaseolus vulgaris): Its specificity in inhibition of mammalian pancreatic .ALPHA.-amylase and formation of a complex with the porcine enzyme.

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Abstract
A proteinaceous inhibitor that inhibits mammalian .alpha.-amylases was prepared from cranberry bean and examined for its reactivity with .alpha.-amylases from various origins. The cranberry bean .alpha.-amylase inhibitor (CBAI) exhibited inhibitory effects on pancreatic .alpha.-amylases from the following mammals: pig, dog, cat, horse, sheep, cow, rabbit, guinea pig, rat and mouse. CBAI showed a maximal inhibition at pH 5.5 against porcine pancreatic .alpha.-amylase (PPA). It was confirmed by gel filtration that a complex was formed in the 1:1 ratio between CBAI and PPA when they were incubated at 37.degree. C for 30 min at pH 5.5. A similar inhibition pattern was also observed at pH 6.9 that is optimal for the amylase reaction, but much higher concentrations of CBAI were required to give 50% inhibition at pH 6.9 than at pH 5.5. Especially, both bovine and rat .alpha.-amylases were virtually unreactive to CBAI at pH 6.9.