Proteolytic activity of an antibody light chain.
The light chain (L chain) of a mAb raised against unactivated vasoactive intestinal peptide (VIP) hydrolyzed this peptide, whereas the heavy chain (H chain) and an irrelevant L chain were without activity. The reaction kinetics were consistent with efficient substrate recognition by the anti-VIP L chain compared with conventional proteases. The L chain cleaved four peptide bonds clustered between residues 16 and 21 in VIP. Mixtures of the L chain with its H chain partner displayed reduced hydrolytic activity compared with the free L chain, suggesting that the H chain is a modulator of the catalytic activity. These observations suggest: 1) the immune system can generate catalytic sites in the L chain subunit of Abs found in response to polypeptide Ags, and 2) free L chains found in vivo could display an Ag-specific catalytic function.
Department of Anesthesiology, University of Nebraska Medical Center, Omaha 68198.
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Paul
D000595:Amino Acid Sequence; D000818:Animals; D017151:Antibodies, Catalytic / Q000502:physiology*; D000911:Antibodies, Monoclonal / Q000502:physiology; D010450:Endopeptidases / Q000276:immunology; D007143:Immunoglobulin Heavy Chains / Q000502:physiology; D007147:Immunoglobulin Light Chains / Q000502:physiology*; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D014660:Vasoactive Intestinal Peptide / Q000276:immunology / Q000378:metabolism
D017151:Antibodies, Catalytic; D000911:Antibodies, Monoclonal; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D014660:Vasoactive Intestinal Peptide; D010450:Endopeptidases