title: Assay and properties of IgA protease of Streptococcus sanguis.
abstract: An assay procedure for streptococcal IgA protease is described which uses isotopically labelled human serum IgA as substrate. Enzyme activity was monitored by the radioactive counts in the Fab alpha product, which was separated from other components in the digestion mixture by electrophoresis. Cleavage of IgA was linear with respect to time using catalytic amounts of the enzyme. Km was calculated to be 5.5 X 10(-6)M, pH optimum 6.0-7.0 at 37 degrees C, and the enzyme was fully inactivated at low concentrations of the metal chelator ethylenediaminetetraacetic acid.
mesh_terms: D004492:Edetic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007070:Immunoglobulin A / Q000378:metabolism*; D007700:Kinetics; D008722:Methods; D009194:Myeloma Proteins / Q000378:metabolism; D010447:Peptide Hydrolases / Q000032:analysis / Q000378:metabolism*; D011480:Protease Inhibitors; D013298:Streptococcus sanguis / Q000201:enzymology*
chemical_list: D007070:Immunoglobulin A; D009194:Myeloma Proteins; D011480:Protease Inhibitors; D004492:Edetic Acid; D010447:Peptide Hydrolases