AN ANTIBODY WITH DUAL CATALYTIC ACTIVITY

Antibodies raised to the bovine serum albumin conjugate of the adduct of acetoxybutadiene with N-(4-carboxybutanoyl)maleimide have been show n to catalyse the Diels-Alder cycloaddition of acetoxy-butadiene with N-benzyl- and N-ethyl-maleimide. For one antibody, designated H11, the reaction was selective for 1-acetoxybutadiene; 1-methoxybutadiene and penta-2,4-diene were not substrates. Product inhibition was not obser ved but the reaction was found to be pH dependent showing a maximum ra te at pH 8.5. Analysis of the products of cycloaddition catalysed by H 11 indicated that the expected acetoxy adduct was obtained but underwe nt further reaction catalysed by H11 to afford the corresponding alcoh ol. This unexpected discovery of a dual catalytic activity associated with an antibody is discussed in the context of hydrolysis reactions c atalysed by antibodies.