A possible hydrolysis mechanism of β-naphthyl acetate catalyzed by antibodies

摘要

The mechanism of ester hydrolysis has bee nexten- sively studied; however, the precise function of active-site residues in promoting catalysis is unclear. We describe here the structural models for the complex of a catalytic antibody Fv fragment with a phosphonate transition-state analogue, constructed by using gene cloning, sequencing and molecular modeling, mainly based on a known X-ray structure of a catalytic antibody. Hydrophobic and elec- trostatic analyses of the Fv/analog and Fv/substrate in- teraction suggest the hydrolysis mechanism: Tyr L91 and Tyr H97 play important roles to stabilize the β-naphthyl group of hapten through π-stack; His H35 donates a pair of free electrons at the atom NE2 to an active water and let is to be a partial hydroxide, which attacks the carbon atom of the carbonyl group of the substrate.