Expression of a functional scFv fragment of an anti-idiotypic antibody with a β-lactam hydrolytic activity

The single chain variable fragment (scFv) of an anti-idiotypic catalytic monoclonal antibody, 9G4H9, displaying a β-lactamase-like activity was cloned. The recombinant protein was expressed through the periplasm in Escherichia coli in the presence or in the absence of FkpA, a chaperone-like enzyme and tested for its hydrolytic activity. The results show that the catalytic parameters for hydrolysis of ampicillin by scFv9G4H9 are clearly influenced by the presence of FkpA, indicating that the correct folding of the fragment represents a crucial step for catalysis.