A common food additive (E452), hexametaphosphate, denatures the digestive enzyme trypsin

Abstract

Phosphate additions in processed foods are a health risk that has been overlooked. This study examined the effects of a permitted food additive (E452; Sodium Hexametaphosphate (SHMP)) on trypsin solubility, structure, and stability at the intestinal physiological pH of 6.0. SHMP-treated trypsin samples were assessed for conformational changes and aggregation propensity using various spectroscopic and microscopic methods. Far-UV CD spectroscopy and intrinsic tryptophan fluorescence showed a rise in fluorescence intensity and alpha-helical structure up to 10 μM SHMP (∼1:1 M ratio). Secondary structure loss, tryptophan quenching, and solubility decrease with an increase in SHMP concentration (>10 μM). SHMP-treated trypsin aggregates showed poor ThT fluorescence. According to kinetics, SHMP leads to trypsin aggregation instantly. All spectroscopic studies showed trypsin denatured at above 10 μM SHMP. Thus, digestive enzyme structure and solubility loss will impair food digestion and health. Therefore, SHMP should be avoided as a food additive.