Approaches to the design of semisynthetic metal-dependent catalytic antibodies

The binding site of the Fab fragment of antibody MOPC315 was chemically modified with cyclam (1,4,8,11-tetraazacyclotetradecane) and 1,10-phenanthroline. In the presence of the metal ions cobalt(II), copper(II), gallium(III), iron(II), nickel(II), zinc(II), these semisynthetic antibodies did not catalyse the hydrolysis of amides or phosphate ester substrates, or the oxidation of a 1-hydroxy-2-alkene or of 3,4-dihydrobenzamide substrates. Hydrolysis of a coumarin ester substrate was catalysed by the Fab derivatized with a cyclam moiety with a kcat of 0.063 min-1 and Km of 11.7 microM; the presence of metal ions was not required for catalysis.