Braun C, Brayer G D, Withers S G
Department of Chemistry, University of British Columbia, Vancouver, Canada.
J Biol Chem. 1995 Nov 10;270(45):26778-81. doi: 10.1074/jbc.270.45.26778.
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 alpha-glucosidase with a second order rate constant of ki/Ki = 0.25 min-1 mM-1. The equivalent difluoromaltoside inactivates human pancreatic alpha-amylase with ki/Ki = 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 alpha-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.
2-脱氧-2,2-二氟糖苷是一类新型的基于机制的α-糖苷酶抑制剂，其通过稳定的二氟糖基-酶中间体的积累发挥作用。已合成了这类新型抑制剂的两个成员，并对其靶标糖苷酶进行了动力学研究。因此，2,4,6-三硝基苯基2-脱氧-2,2-二氟-α-葡萄糖苷被证明能使酵母α-葡萄糖苷酶失活，其二级速率常数ki/Ki = 0.25 min⁻¹ mM⁻¹。等效的二氟麦芽糖苷能使人类胰腺α-淀粉酶失活，ki/Ki = 0.0073 min⁻¹ mM⁻¹。在每种情况下，竞争性抑制剂都能保护酶不被失活，表明反应发生在活性位点。在人类胰腺α-淀粉酶失活时观察到一当量三硝基苯酚盐的快速释放，证明了所需的1:1化学计量比。这些是首次描述的这类基于机制的抑制剂，也是首次针对医学上重要的α-淀粉酶的任何类型的基于机制的抑制剂。除了具有作为治疗剂的潜力外，这类化合物在这些酶的后续结构和机制研究中应该会被证明是有用的。
