Mechanism of heat-induced gelation of pressurized actomyosin: pressure-induced changes in actin and myosin in actomyosin

The biochemical and physicochemical changes of myosin (myosin A), actomyosin (natural actomyosin), and actin after pressure treatment were investigated to elucidate the cause of the increased gel strength of pressurized actomyosin. Analysis of DNase I inhibition capacity of actomyosin demonstrated that in buffers containing 0.6 M KCI most of the actin in actomyosin was denatured by pressures of 150 MPa. However, at KCl concentrations greater than 0.6 M, a large part of actin in actomyosin was found to exist as the depolymerized form (native G-actin) after the release of pressure. Mg2+-ATPase activity of actomyosin decreased with increasing pressure, whereas Ca2+-ATPase activity was not affected at pressures below 200 MPa. Both sulfhydryl (SH) content and surface hydrophobicity of actomyosin increased with an increase in pressure. In conclusion, pressure effects on the heat-induced gelation of actomyosin are attributable to the denaturation of actin in actomyosin and the increased SH content and surface hydrophobicity