Cathepsin G from human polymorphonuclear leukocytes cleaves human IgM.
Cathepsin G, the chymotrypsin-like enzyme from human polymorphonuclear leukocytes, cleaves human IgM and produces two major fragments that closely resemble those released by leukocyte elastase digestion of IgM. An F(ab)2 mu-like fragment, mol. wt 140,000, retains some reactivity with an anti-Fc mu antiserum and is antigenically deficient with respect to the IgM subunit. The other fragment is an Fab mu-like product with a mol. wt of 54,000. Both cathepsin G fragments are indistinguishable from the elastase counterparts by immunochemical analysis. An Fc mu fragment could not be recovered. The kinetic course of the cleavage shows that cathepsin G produces Fab mu fragments at a higher rate than F(ab)2 mu, whereas the contrary is valid for elastase. Beside the two major fragments and low mol. wt peptides, cathepsin G releases also a product with the same mol. wt and immunological reactivity as the IgM subunit. The biological significance of the interaction between IgM and leukocyte proteinases is discussed.
D000911:Antibodies, Monoclonal / Q000378:metabolism; D056649:Cathepsin G; D002403:Cathepsins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007128:Immunoglobulin Fragments / Q000032:analysis; D007075:Immunoglobulin M / Q000378:metabolism*; D009504:Neutrophils / Q000201:enzymology*; D010196:Pancreatic Elastase / Q000378:metabolism; D012697:Serine Endopeptidases
D000911:Antibodies, Monoclonal; D007128:Immunoglobulin Fragments; D007075:Immunoglobulin M; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D010196:Pancreatic Elastase