Characterisation of the group 4 allergens from the house dust mite

[Truncated] Background: The group 4 allergen was first isolated from the house dust mite (HDM) species Dermatophagoides pteronyssinus by Lake et al. (1991) and found to be physicochemically similar to mammalian a-amylase with a molecular weight (MW) of 60000, heterogeneous isoelectric points ranging between 5 and 7, the capacity to digest starch and bind to an organomercurial affinity matrix. This natural Der p 4 was shown in Western blotting studies to bind IgE in the serum of 46% of mite allergic adults and 25% of mite allergic children.

Results: The cDNA encoding Der p 4 and it's homologue in Euroglyphus maynei were isolated by screening the respective cDNA libraries and sequenced. The aa sequences of Der p 4 and Eur m 4 were 90% identical and encoded 496 amino acid (aa) mature proteins with 25 and 27 aa signal peptides respectively. The calculated MW of the proteins was 57000. A single N-glycosylation site was present in Der p 4 and Eur m 4. The sequences were approximately 50% identical to other α-amylases from insects and mammals and contained highly conserved primary sequences known to be critically important for α-amylase function, confirming the identity of these proteins as α-amylase enzymes.