Mechanism of the binding of Z-L-tryptophan and Z-L-phenylalanine to thermolysin and stromelysin-1 in aqueous solutions

► The side chain of Z-Trp is not bound in the S2′ subsite of thermolysin. ► The inhibitor carboxylate groups bind to the catalytic zinc of both enzymes. ► The inhibitor carboxylate pKas are reduced by ≥1.5 pKa units on enzyme binding. ► Z-Trp or Z-Phe induce tetrahedral coordination of the metal in thermolysin.