title: Purification and characterization of an immunoglobulin A1 protease from Bacteroides melaninogenicus.
abstract: Attention has recently been focused on bacterial proteases with the capacity to cleave immunoglobulin A (IgA proteases) as possible pathogenic factors in bacterial meningitis, gonorrhoea, and destructive periodontal disease. Here, we describe a method for the rapid purification of a specific IgA1 protease from Bacteroides melaninogenicus. The IgA1 protease was purified 6,172-fold with a yield of 9% by ammonium sulfate precipitation, DEAE-ion exchange chromatography, and separation on a preparative TSK-G 3000SWG high-pressure gel permeation chromatography column. The enzyme was specific for human IgA1 and cleaved a prolyl-seryl peptide bond in the hinge region of the alpha 1 chain between residues 223 and 224. The molecular weight of the enzyme was 62,000, the isoelectric point was 5.0, and the Km was 3.4 X 10(-6). The enzyme was active over a broad pH range and had maximal activity at pH 5.0. B. melaninogenicus IgA1 protease was classified as a thiol protease on the basis of its inhibition by traditional protease inhibitors and the fact that it was active only under reducing conditions.
mesh_terms: D001439:Bacteroides / Q000201:enzymology*; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000302:isolation & purification*; D001443:Prevotella melaninogenica / Q000201:enzymology* / Q000276:immunology; D011480:Protease Inhibitors; D012697:Serine Endopeptidases; D013379:Substrate Specificity
chemical_list: D011480:Protease Inhibitors; D010447:Peptide Hydrolases; D012697:Serine Endopeptidases; C021433:IgA-specific serine endopeptidase