DIFFERENCES IN THE BIOCHEMICAL-PROPERTIES OF ESTEROLYTIC ANTIBODIES CORRELATE WITH STRUCTURAL DIVERSITY

A prerequisite to the design and engineering of catalytic antibodies i s the knowledge of their structure and in particular which residues ar e involved in binding and catalysis. We compared the structure and cat alytic properties of a series of six monoclonal antibodies which were all raised against a p-nitrophenyl (PNP) phosphonate and which catalyz e the hydrolysis of p-nitrophenyl esters. Three of the antibodies (Gro up I) have similar light and heavy chain variable regions. The other t hree antibodies have similar V-L regions of which two (Group II) have V-H regions from the MOPC21 gene family and the remaining one (Group I II) a V-H from the MC101 gene family making a total of three different groups based on their V region sequences. The structural division int o groups is paralleled by the differences in binding constants to hapt en analogs, substrate specificity and the susceptibility of the cataly tic activity of the antibodies to chemical modification of tryptophan and arginine residues. The relative binding of a transition state anal og to the binding of substrate is much higher for the Group I antibodi es than for the other groups. Only the Group I antibodies can catalyze the hydrolysis of a carbonate substrate. However all of the antibodie s lose catalytic activity upon specific tyrosine modification which hi ghlights the importance of tyrosine in the active site of the antibodi es. Thus, antibodies raised against a single hapten can give antibodie s with different structures, and correspondingly different specificiti es and catalytic properties.