Physicochemical properties of natural actomyosin from threadfin bream (Nemipterus spp.) induced by high hydrostatic pressure

Changes of physicochemical properties in natural actomyosin (NAM) from threadfin bream (Nemipterus spp.) induced by high hydrostatic pressure (200, 400, 600 MPa for 10, 30, 50 min) were studied. The increase in turbidity of NAM was coincidental with the decrease in protein solubility with increasing pressure and time, suggesting the formation of protein aggregates. SDS-PAGE showed that polymerisation and degradation of myosin heavy chain were induced by high pressure. Ca2+-ATPase activity of NAM treated by high pressure was lost, suggesting the denaturation of myosin and the dissociation of actomyosin complex. Surface hydrophobicity of NAM increased when the pressure and pressurization time increased, indicating that the exposed hydrophobic residues increased upon application of high pressure. Decrease in total sulfhydryl content and increase in surface-reactive sulfhydryl content of NAM samples were observed with the extension of pressurizing time, indicating the formation of disulphide bonds through oxidation of SH groups or disulphide interchanges. The above changes of physicochemical properties suggested conformational changes of NAM from muscle of threadfin bream induced by high hydrostatic pressure.