摘要
The mechanism of ester hydrolysis has been extensively studied; however, the precise function of active-site residues in promoting catalysis is nuclear. We describe here the structural models for the complex of a catalytic sntibody 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 atibody. Hydrophobic and electrostatic analyses of the Fv/analog and Fv/substrate interaction suggest the hydrolysis mechanism: In L91 and Tyr H97 play important roles to stabilize the β-naphthyl group of hapten through r-stack; His H35 donates a pair of free electrons at the atom NEZ to an active water and let it to be a partial hydroxide, which attacks the carbon atom of the carbonyl group of the substrate. Both His H35 and Arg L96 can form hydrogen bonds and stabilize the Anoinc tetrahedral intermediate formed during turnover. This mechanism emphasizes that an active water bridge may be formed during hydrolysis process.
