| abstract |
A method is provided for preparing a labeled protein, immobilized protein or protein-bioactive agent composition by attaching a label, support or bioactive agent to a protein by exopeptidase catalysis at a site that is remote from the active site of the protein. More specifically, an amine or alcohol group of an amino acid, amine or alcohol nucleophile is reacted by exopeptidase catalysis with a C-terminus carboxylic acid group of a protein such as an antibody, enzyme or hormone to couple the nucleophile to the protein to form an adduct, and the adduct is bound to an auxiliary substance such as a support, label or bioactive agent or its combination with a linker arm by reacting a reactive substituent of the nucleophile with a reactive group of the auxiliary substance. Alternatively, the nucleophile is bound to the auxiliary substance or its combination with a linker arm to form an intermediate, and the intermediate is coupled by exopeptidase catalysis to the protein. The exopeptidase may be a serine or cysteine exocarboxypeptidase. |