Comparison of Recombinant <i>Ctenopharyngodon idella</i> Allergen Parvalbumin, Produced in <i>Pichia pastoris</i> and <i>Escherichia coli</i> : From Structure to Functional Properties

Parvalbumin (PV) is the major allergen in grass carp (<i>Ctenopharyngodon idellus</i>). Recombinant parvalbumins in <i>Escherichia coli</i> (<i>Ec</i>PV) and <i>Pichia pastoris</i> (<i>Pp</i>PV) were successfully expressed, with respective molecular weights of 14 kDa and 16 kDa. Mass spectrometry confirmed the identity of the proteins, while ultraviolet spectroscopy, circular dichroism spectroscopy, and fluorescence spectroscopy were used for structural validation. Physicochemical properties were further evaluated through digestibility assays, sIgE inhibition ELISA, Western blotting, and RBL-2H3 cell degranulation experiments. The results indicated that the recombinant proteins exhibited a high degree of amino acid sequence similarity with the natural protein (<i>Na</i>PV) and shared core immunodominant epitopes, while demonstrating higher IgE-binding efficiency compared to the natural protein. In contrast to <i>Ec</i>PV, <i>Pp</i>PV showed greater resistance to pepsin digestion, displayed differences in secondary structure, and exhibited altered conformational epitopes. Therefore, the degranulation efficiency of RBL-2H3 cells induced by <i>Pp</i>PV was lower than that induced by <i>Ec</i>PV and <i>Na</i>PV.