Enzyme immobilization via monoclonal antibodies I. Preparation of a highly active immobilized carboxypeptidase A

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Abstract
A novel method for the preparation of highly active immobilized enzymes is described. It is based on the binding of enzymes to suitable carriers via monoclonal antibodies, which bind to the enzyme with high affinity without affecting its catalytic activity. The applicability of the method forwarded has been illustrated by the preparation of two samples of highly active immobilized carboxypeptidase A (CPA) preparations as follows: A mouse monoclonal antibody (mAb 100)to CPA that binds to the enzyme with a high-affinity constant without affecting its catalytic activity was prepared, purified, and characterized. Covalent binding of this monoclonal antibody to Eupergit C (EC) or noncovalent binding to Sepharose–protein A (SPA)yielded the conjugated carriers EC-mAb and SPA·mAb, respectively, which reacted specifically with CPA to give the immobilized enzyme preparations EC-mAb·CPA and SPA·mAb·CPA displaying full catalytic activity and improved stability. At pH 7.5 and a temperature range of 4–37°C an apparent binding constant of ∼108M−1 characterizing the interaction of CPA with EC-mAb and SPA·mAb, was obtained. To compare the properties of EC-mAb·CPA and SPA·mAb·CPA with those of immobilized CPA preparations obtained by some representative techniques of covalent binding of the enzyme with a corresponding carrier, the following immobilized CPA preparations were obtained and their properties investigated: EC-CPA (I), a preparation obtained by direct binding of EC with CPA; EC-NH-GA-CPA (II), a derivative obtained by covalent binding of CPA to aminated EC via glutaraldehyde; EC-NH-Su-CPA (III), a CPA derivative obtained by binding the enzyme to aminated EC via a succinyl residue; and EC-HMD-GA-CPA (IV), obtained by binding the enzyme via glutaraldehyde to a hexamethylene diamine derivative of EC. Full enzymic activity for all of the bound enzyme, such as that recorded for the immobilized CPA preparations EC-mAb·CPA and SPA·mAb·CPA, was not detected in any of the insoluble covalently bound enzyme preparations.