Trypsin digestion of protein in beef meat extract in the presence of microplastics

Trypsin is the main protease in the intestine. Microplastics (MPs) have been previously shown to interact with and decrease the activity of some digestive enzymes, including pepsin and lipase. Red meat has been shown to be a source of allergy which has been linked to the galactose-alpha-1,3-galactose (alpha-Gal) post-translational modification of proteins. Our aim was to investigate the effect of two types of MPs commonly found in the environment – polypropylene (PP) and polyethylene terephthalate (PET) – on the digestion of protein in beef meat extract and preservation of protein harboring the alpha-Gal epitope. Digestion of beef meat extract has been performed with trypsin in simulated intestinal fluid (SIF) in the presence of MPs. After digestion was stopped with a specific inhibitor, bulk beef meat extract was separated through centrifugation from the MPs. Soft coronas were obtained by washing the MPs with SIF. The hard corona was obtained by addition of a reducing buffer for electrophoresis sample preparation to the MPs with a heating step at 95°C. All samples were analyzed with SDS-PAG electrophoresis. Selected samples were further analyzed with anti-alpha-Gal antibodies using western blot. There is an observable difference between the digestion patterns of meat extract after 1 and 2 h of digestion in the presence of MPs compared to the control. Evolution of digestion is similar for both types of MPs, without regard to plastic type. It has also been confirmed that preserved proteins possess the alpha-Gal modification. As MPs presence does not change trypsin specific activity, the change in digestion pattern is presumed to be due to steric effects and/or interplay of enzyme/protein in the corona. This study suggests that MPs presence influences trypsin digestibility of meat proteins, including alpha-Gal-bearing allergens.