X-ray structures of two families of hydrolytic antibodies

The catalytic mechanisms of two esterase-like catalytic antibodies (Abs) ha ve been determined, based on kinetic data and on structures of the complexe s with transition-state analogs and with a stable substrate analog of the r eactions they catalyze. Both Abs stabilize the oxyanion intermediate close to the transition state in eater hydrolysis. The different geometries of th e hydrogen bonds that participate in this stabilization account for most of the difference between the efficiencies of these two Abs.