CATALYTIC PROPERTIES OF THE ANTIBODY H11

The catalytic activity of the antibody H11 is shown to reside chiefly in its ability to hydrolyze 1-acetoxybutadiene to crotonaldehyde and t o promote the cycloaddition of the intermediate enol with N-alkylmalei mides. This conclusion is based upon the demonstration that the enol t automerizes too rapidly in solution to be a competent intermediate and that under the reaction conditions for H11, no cycloaddition occurs w ith crotonaldehyde and N-ethylmaleimide. As a first step towards a str uctural understanding of the chemistry of H11, chemical modification e xperiments have shown that reactions of acidic amino acids, tyrosine, lysine, and histidine, but not arginine, inhibit the reactions mediate d by H11.