The isolation and characterization of a novel collagenolytic serine protease allergen (Der p 9) from the dust mite Dermatophagoides pteronyssinus.

BACKGROUND

Dust mites have been shown to contain a serine protease distinct from the previously reported trypsin and chymotrypsin. The latter enzymes have been shown to be allergens, but the allergenic importance of the former is unknown.

OBJECTIVE

This study was performed to isolate and characterize the novel mite serine protease and determine its allergenicity.

METHODS

The mite serine protease was isolated from feces-enriched extracts of Dermatophagoides pteronyssinus by ion-exchange chromatography and affinity chromatography, and its physicochemical properties were determined. The allergenicity of the protease was assessed by using the RAST.

RESULTS

The protease was enzymatically similar to chymotrypsin and cathepsin G-like enzymes from a variety of sources and was shown to cleave collagen. It had a molecular mass of 23,780 d. N-terminal sequence analysis (18 residues) indicated homology with the mite tryptic allergen, Der p 3, and the chymotryptic allergen, Der p 6. RAST analyses showed that the frequencies of reactivity to the novel allergen and to Der p 1, Der p 2, Der p 3, and Der p 6 were 92%, 97%, 100%, 97%, and 65%, respectively (n = 35). RAST inhibition studies showed some cross-reactivity between the protease and Der p 3 but not Der p 6.

CONCLUSIONS

A novel mite serine protease was isolated from D. pteronyssinus and found to be a major allergen. This allergen has been tentatively designated Der p 9.