The nonreducing end of the substrate-binding site of human salivarya-amylase contains two residues Trp58 and Trp59, which belong tob2–a2 loop of the catalytic (b/a)8 barrel. While Trp59 stacks onto the substrate, the exact role of Trp58 is unknown. To investigate its role in enzyme activity the residue Trp58 was mutated to Ala, Leu or Tyr. Kinetic analysis of the wild-type and mutant enzymes was carried out with starch and oligosaccharides as substrates. All three mutants exhibited a reduction in specific activity (150–180-fold lower than the wild type) with starch as substrate
