Efficient heterologous expression, functional characterization and molecular modeling of annular seabream digestive phospholipase A2

Anatomy, immunology, digestive physiology and microbiota of the salmonid intestine: Knowns and unknowns under the impact of an expanding industrialized production

Increased industrialized production of salmonids challenges aspects concerning available feed resources and animal welfare. The immune system plays a key component in this respect. Novel feed ingredients may trigger unwarranted immune responses again affecting the well-being of the fish. Here we review our current knowledge concerning salmon intestinal anatomy, immunity, digestive physiology and microbiota in the context of industrialized feeding regimes. We point out knowledge gaps and indicate promising novel technologies to improve salmonid intestinal health.

Intestinal phospholipase A2 from Sparidae species: Functional properties and cytotoxic potential evaluation

Marine species have gained significant attention as potential source for a broad spectrum of bioactive proteins. Fish phospholipases A₂ (PLA₂) have attracted renewed interest due to their excellent properties in lipid digestion. Herein, we report for the first time the catalytic properties of two intestinal secreted PLA₂ (sPLA₂) identified from Diplodus sargus (IDsPLA₂) and Sparus aurata (ISaPLA₂). The highest sequence identity was obtained with recently isolated Sparidae digestive PLA₂ (45%) and Human pancreatic PLA₂ (42%). IDsPLA₂ and ISaPLA₂ were overexpressed in E. coli as inclusion bodies, refolded and purified. Both enzymes have improved thermostability compared to mammalian pancreatic sPLA₂ since they are active and stable at 55 °C, with specific activities of 320 and 190 U mg^-1 measured on phosphatidylcholine, respectively. Interestingly, IDsPLA₂, but not ISaPLA₂, revealed weak toxicity towards macrophages and suggests its involvement in cell membrane degradation. ISaPLA₂ was found to be more active than IDsPLA₂ when using the monolayer technique at 20 mN m^-1. Structural models of both enzymes revealed their differences. In silico docking of phospholipids with both models allowed proposing key amino-acids in substrate binding and selectivity. Overall, these results provide insight into the enzymatic and structural properties of two novel sPLA₂ with potential for future applications.