Heterogeneous proteolytic specificity and activity of the house dust mite proteinase allergen Der p I.
BACKGROUND
Exposure of the skin or respiratory tract to proteinases is frequently associated with allergic sensitization. This is of particular significance in the domestic indoor environment where the proteolytic activity of Der p I, the group I allergen of the house dust mite Dermatophagoides pteronyssinus, may influence the allergenicity of mites. Using class-specific proteinase inhibitors and active-site affinity chromatography, we have previously shown that Der p I exhibits a mixed cysteine-serine proteinase activity. Measurement of the amount of cleavage, however, did not determine whether the inhibitors used were targeting exactly the same proteolytic mechanism.


OBJECTIVE
To resolve this issue, we have examined whether the cleavage specificity of the cysteine and serine proteinase activities of Der p I was the same.


METHODS
HPLC and mass spectrometry were used to analyse and identify the products of a Der p I-digested peptide substrate and thus identify the peptide bonds cleaved.


RESULTS
Der p I cleaves different peptide bonds, depending upon the class of proteolytic mechanism used. In the model peptide substrate insulin B chain, the cysteine and serine proteinase activities of Der p I showed preference for glutamic acid and arginine respectively in the P1 position.


CONCLUSIONS
These data suggest the existence of more than one mechanistic form of the allergen immunologically identified as Der p I. If proteolytic activity is indeed a function of allergenicity, this information may have important implications for the pathogenicity of Der p I and the ability of innate antiproteinase defences in the respiratory tract to prevent immune sensitization.
Hewitt
C R
CR
Immunotoxicology Laboratory, MRC Toxicology Unit, University of Leicester, UK.
Horton
H
H
Jones
R M
RM
Pritchard
D I
DI
D000485:Allergens / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D039741:Antigens, Dermatophagoides; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors; D001665:Binding Sites; D002384:Catalysis; D006023:Glycoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors; D008925:Mites / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D008969:Molecular Sequence Data; D012697:Serine Endopeptidases / Q000276:immunology* / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity / Q000276:immunology
D000485:Allergens; D039741:Antigens, Dermatophagoides; D006023:Glycoproteins; D015842:Serine Proteinase Inhibitors; D012697:Serine Endopeptidases; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases