MECHANISM-BASED INHIBITION OF YEAST ALPHA-GLUCOSIDASE AND HUMAN PANCREATIC ALPHA-AMYLASE BY A NEW CLASS OF INHIBITORS - 2-DEOXY-2,2-DIFLUORO-ALPHA-GLYCOSIDES

2-Deoxy-2,2-difluoroglycosides are a new class of mechanism-based inhibitors of alpha-glycosidases, which function via the accumulation of a stable difluoroglycosyl-enzyme intermediate. Two members of this new class of inhibitor have been synthesized and kinetic studies performed with their target glycosidases. Thus 2,4,6-trinitrophenyl 2-deoxy-2,2-difluoro-alpha-glucoside is shown to inactivate yeast a-glucosidase with a second order rate constant of k(i)/K-i = 0.25 min(-1) mM(-1). The equivalent difluoromaltoside inactivates human pancreatic cu-amylase with k(i)/K-i = 0.0073 min(-1) mM(-1). Competitive inhibitors protect the enzyme against inactivation in each case, showing reaction to occur at the active site. A burst of release of one equivalent of trinitrophenolate observed upon inactivation of human pancreatic a-amylase proves the required 1:1 stoichiometry. These are the first mechanism-based inhibitors of this class to be described, and the first mechanism-based inhibitors of any sort for the medically important alpha-amylase. In addition to having potential as therapeutics, compounds of this class should prove useful in subsequent structural and mechanistic studies of these enzymes.