A myosin heavy chain degradation inhibitor (MDI) prepared from the sarcoplasmic protein of a particular fish meat inhibited the serine protease (trypsin, chymotrypsin) activity. The degradation of myosin heavy chain in the washed meat around 40°C was also restrained by adding serine protease inhibitors. It is therefore conceivable that MDI is water soluble and acts as an inhibitor against serine protease in washed meat.
MDI was isolated from the water soluble fraction of fish meat through a 4-step process, batch type DEAE ion exchange, ammonium sulfate fractionation, DEAE ionexchange chromatography, and Sephacryl S-300 gel filtration chromatography. It was found to be a monomeric protein with a molecular weight of 80,000.