Treatment of Immunoglobulins with Proteolytic Enzymes

Treatment of Immunoglobulins with Proteolytic Enzymes

The immunoglobulin molecule can be broken into a number of “sections” or “fragments” by action of proteolytic enzymes. The proteolytic enzyme papain cleaves just above the interchain disulfide bonds linking the heavy chains, whereas the enzyme pepsin cleaves just below these bonds, thereby generating different digestion products. For example, peptide bonds in the “hinge” region are broken on treatment of antibody molecule with papain, resulting in production of two iden-tical Fab fragments and one Fc fragment. The Fab frag-ments produced during cleavage monovalently bind to the antigen. Treatment with pepsin cleaves immunoglobulin but at a different site, producing an Fc fragment and two Fab fragments, F (ab)₂, which upon exposure to reducing conditions are separated into Fab monomeric units.