Diversity and Relative Levels of Actinidin, Kiwellin, and Thaumatin-Like Allergens in 15 Varieties of Kiwifruit (<i>Actinidia</i>)

In the last 30 years the incidence of kiwifruit allergy has increased with the three major allergenic proteins being identified as actinidin, kiwellin, and thaumatin-like protein (TLP). We report wide variation in the levels of actinidin and TLP in 15 kiwifruit varieties from the four most widely cultivated <i>Actinidia</i> species. Acidic and basic isoforms of actinidin were identified in <i>Actinidia deliciosa</i> ‘Hayward’ and <i>Actinidia arguta</i> ‘Hortgem Tahi’, while only a basic isoform of actinidin was identified in <i>Actinidia chinensis</i> ‘Hort16A’. One isoform each of kiwellin and TLP were identified in ripe fruit. The cysteine protease activity of actinidin correlated with protein levels in all species except <i>A. arguta</i>. Protein modeling suggested that modifications to the S2 binding pocket influenced substrate specificity of the <i>A. arguta</i> enzyme. Our results indicate that care is necessary when extrapolating allergenicity results from single varieties to others within the same and between different <i>Actinidia</i> species