Identification of parvalbumin as an allergen in horse mackerel [Trachurus japonicus] muscle

The crude extracts from the white muscle of five species of fish (horse mackerel Trachurus japonicus, Pacific mackerel Scomber japonicus, bigeye tuna Thunnus obesus, chum salmon Oncorhynchus keta, walleye pollack Theragra chalcogramma) were evaluated for allergenicity by enzyme-linked immunosorbent assay(ELISA) using sera from two fish-allergic patients. All the extracts reacted with the IgE antibodies in one patient serum; the highest reaction was given by the horse mackerel extract and the lowest reaction by the bigeye tuna extract. In contrast, the bigeye tuna was the only positive sample as analyzed using another patient serum. Based on ELISAs using the former patient serum, a heat-stable allergen (named Tra j 1) in the horse mackerel was isolated by gel filtration on Sephadex G-75 and reverse-phase HPLC on TSKgel ODS-120T. In SDS-PACE, Tra j 1 gave a single band corresponding to a molecular weight of 10,500, regardless of the presence or absence of a reducing agent. The isoelectric point of Tra j 1 was estimated to be 4.3 by IEF-PAGE. Tra j 1 was rich in Ala, followed by Asx and Lys, but lacked Cys(half), His, and Trp. Furthermore, it showed an ability to bind to the monoclonal antibody against carp parvalbumin. From these physicochemical and immunological properties, Tra j 1 was identified as parvalbumin of the horse mackerel.