Labeling and label free shotgun proteomics approaches to characterize muscle tissue from farmed and wild gilthead sea bream (Sparus aurata)

• Shotgun proteomics was employed to characterize farmed and wild fish edible parts.
• Label free and dimethyl labeling quantification were compared for fish analysis.
• Label free shotgun proteomics provided the best results for fish proteome profiling.
• The main fish allergen parvalbumin was significantly overexpressed in farmed fish.

The proteome characterization of fish muscle tissues, together with the relative expression of each individual protein, provides knowledge on the biochemical response of the organisms and allows to assess the effect of different types of feeding, growth site and nutritional quality of the investigated species. This type of study is usually performed by gel-based proteomics approaches, however shotgun proteomics can serve as well, reducing analysis time and improving sample high-throughput. In this work, a shotgun proteomics method was thus developed and then applied to the characterization of gilthead sea bream edible muscle. The sarcoplasmic protein fraction was extracted, in-solution digested by trypsin and finally analyzed by nanoHPLC high resolution tandem mass spectrometry. Two different quantification strategies were also tested. One was based on chemical dimethyl labeling and the other one on label free quantification. A comparison between these two analytical workflows was performed, to evaluate their individual performance in the analysis of fish samples and assess the differences induced by farming practice on the final commercial product with respect to wild gilthead sea bream. Quantitative differences were detected, and the most relevant one regarded the common fish allergen parvalbumin, found overexpressed in farmed fish samples.