Partial purification and comparison of precipitation techniques of proteolytic enzymes from trout (Salmo gairdnerii) heads

Proteolytic enzymes have been detected and partially purified from trout (Salmo gairdnerii) heads, which were preserved at −20 °C. Proteolytic enzymes, either in crude extract or in partial purified samples, were stable for 15 days with an optimum temperature of 55 °C. Proteolytic activity was very high in either alkaline or acidic pH regions. A particular ratio of cold acetone to crude extract (1.25:1) was found to be best for the partial purification of proteases, with a 99% recovery, compared with the partial purifications achieved using different cold acetone ratios or ammonium sulphate. This recovery was also confirmed via measurement of the particles (particle size analyser) contained either in crude extract or in the precipitated samples. The existence of mainly Zn–serine and possibly some Zn-acidic proteases was observed.