Citation

Angeles TS, Martin MT. Biochem. Biophys. Res. Commun. 1993; 197(2): 696-701.

Copyright

(Copyright © 1993, Academic Press)

DOI

10.1006/bbrc.1993.2535

PMID

8267606

Abstract

Studies of alternative substrates of the catalytic monoclonal antibodies 18H4, 7D4, and 45A11 provided us with a better understanding of the mechanism of ester hydrolysis employed by these isoabzymes. The antibodies were studied with analogs of the substrate, phenyl acetate; N-acetylglycine phenyl ester 3 and N-carbobenzoxy-glycine phenyl ester 4. All three antibodies catalyzed 3 hydrolysis with kinetic constants similar to those seen with phenyl acetate hydrolysis. However, 4 was found to be a mechanism-based (suicide) inactivator of 18H4 with a kinact of 0.29 min-1 and a K' of 64 microM. Antibody 18H4 was inactivated by 4 after 3.6 turnovers resulting in the acylation of 1.6 tyrosines per combining site. The data conform to a mechanism in which an inactive O-ZGly-tyrosyl-antibody is formed via a Michaelis complex.

Language: en

Keywords

Antibodies, Monoclonal; Catalysis; Esters; Hydrolases; Hydrolysis; Kinetics; Substrate Specificity; Time Factors