Studies on the denaturation of muscle proteins under high pressure.

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The denaturation of muscle proteins under high pressure was investigated by histological, biochemical and physicochemical methods.Actin1) The rate of dissociation of nucleotides from actin molecule, disappearance of the characterized ^1H NMR signal at 2.055 ppm and loss in biochemical activities (DNAasel inhibition capacity, polymerizability) at 300 MPa were almost identical. suggesting that the rapid collapse of steric structure around the upper region called "pointed end" of actin molecule following the dissociation of the bound nucleotide.2) The decreases of α-helix content were observed with the pressure applied and the denaturation was irreversible in the actin pressurized at 300 MPa or more.Myosin and Tropomyosin1) The structural changes in myosin molecule pressurized at 200 MPa or more were irreversible.2) Tropomyosin which is resistive to acid and heat was also resistive to high pressure.Mitochondria and Connective Tissue1) The decrease of Ca^<2+> uptaking ability seemed to be correlated with the decrease of ATPase activity which may be caused by the release of ATPase subunits (α β) from mitochondria by pressure.2) The deformation of the honeycomb-like structure of endomysium was accelerated with increase of pressure applied, but the changes in the extractability of PGs were not observed in the pressurized muscle.ProteasomeThe high pressure treatments up to 50〜100MPa caused the activation of the proteasome. This activation is probably due to the increase of the interaction of the substrate and active site of the proteasome unfolded by high pressure treatment.β-Lactoglobulin (BLg) and High Pressure-Thawing1) No difference in the ^1NMR spectrum was observed between pressurized and unpressurized BLg. NMR detection of the H/D exchange of aromatic residues indicated that the conformation at the vicinity of tryptophan residues can be refolded after the release of pressure.2) It was cleared that the high pressure-thawing was applicable to meat processing.