Sodium pyrophosphate-induced actomyosin dissociation, thick filament depolymerization and protein conformation...

Mechanism of sodium pyrophosphate (TSPP) enhancing myofibrillar protein solubility remains unclear. This study investigated effects of TSPP on myofibrillar protein structures and physicochemical properties. With increasing TSPP concentration, the bound phosphorus content, absolute zeta-potential, and actomyosin dissociation of myofibrillar protein significantly increased. P₂O₇^4- preferentially bound to Lys-638 and Lys-642 in the ATP-binding loop of myosin S1 fragment, thereby modulating myosin-actin dissociation. PO₄^3- generated from P₂O₇^4- hydrolysis preferentially bound to Lys-1878 and Lys-1883 of myosin LMM fragment, disrupting the assembly function of assembly competence domain (ACD) and the periodic charge distribution along LMM fragment, thus promoting thick filament disassembly. TSPP treatment altered the spatial conformation of myofibrillar protein, as evidenced by decreased tryptophan fluorescence, and increased surface hydrophobicity, surface sulfhydryls and intermolecular interactions. The actomyosin dissociation, thick filament disassembly and conformational changes collectively improved protein solubility. Results provide a theoretical basis for meat quality improvement strategies based on protein structure modulation.