Denaturation of Enzyme Protein by Freeze-Thawing and Freeze-Drying ; I. Freeze-thawing and freeze-drying of myosin and some other muscle proteins

Changes in physico-chemical properties and m enzymatic activities of some muscle proteins by freeze-thawing or freeze-drying were measured for the purpose of clarifying the mechanism of protein denaturation by freeze-thawing and freezedrying. The results showed following: Freeze-thawing unfolded the conformation of the rod-like proteins and decreased their enzymatic activities. The two effects increased with the lowering of the final freezing temperature as well as with the slowing of the cooling rate. Freeze-drying unfolded the protein molecules more than freeze-thawing did. Some additives such as sugars or amino acids protected the protein against denaturation by freezing. The effects of freeze-thawing seemed to depend on the shape of the protein molecule. It was suggested that protein denaturation by freeze-thawing might be basically due to the crystallization of solvent water which loosened the hydrophobic bonds of the protein molecules and which broke the intramolecular hydrogen bonds in such a manner that the hydration shell of protein was disturbed.