The B12 anti-tryptase monoclonal antibody disrupts the tetrameric structure of heparin-stabilized beta-tryptase to form monomers that are inactive at neutral pH and active at acidic pH.
The novel tetrameric structure of human beta-tryptase faces each active site into the central pore, thereby restricting access of most biologic protease inhibitors. The mechanism by which the anti-tryptase mAb B12 inhibits human beta-tryptase peptidase and proteolytic activities at neutral pH, but augments proteolytic activity at acidic pH, was examined. At neutral pH, B12-beta-tryptase complexes are inactive. At acidic pH, B12 (intact and Fab) minimally affects peptidase activity when added to beta-tryptase tetramers, but does induce susceptibility to inhibition by soybean trypsin inhibitor and antithrombin III. Surprisingly, B12 Fab-beta-tryptase complexes formed at both neutral and acidic pH exhibit the apparent molecular mass of a complex with 1 beta-tryptase monomer and 1 Fab by gel filtration. B12 does not compete with heparin for binding to tryptase at either neutral or acidic pH. Thus, B12 directly disrupts beta-tryptase tetramers to monomers that are inactive at neutral pH, whereas at acidic pH, are active and more accessible to protein inhibitors and substrates.
Fukuoka
Yoshihiro
Y
Division of Rheumatology, Allergy and Immunology, Department of Internal Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA.
Schwartz
Lawrence B
LB
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D016264:Dextran Sulfate; D004789:Enzyme Activation / Q000276:immunology; D004795:Enzyme Stability / Q000276:immunology; D005340:Fibrinogen / Q000378:metabolism; D006493:Heparin / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051379:Mice; D020836:Protein Structure, Quaternary; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D013552:Swine; D053802:Tryptases
D000911:Antibodies, Monoclonal; D015842:Serine Proteinase Inhibitors; C509190:Tpsb2 protein, mouse; D005340:Fibrinogen; D006493:Heparin; D016264:Dextran Sulfate; D012697:Serine Endopeptidases; C509222:Tpsab1 protein, mouse; D053802:Tryptases