Distribution of Cathepsin D Activity between Lysosomes and a Soluble Fraction of Marinating Brine

This paper is the first ever to describe the phenomenon of bimodal distribution of cathepsin D in the lysosomal and soluble fractions of brine left after herring marinating. Up to 2 times higher cathepsin D activity was observed in the lysosome fraction. Activity of cathepsin D in brine increased according to the logarithmic function during low frequency-high power ultrasounds treatment or according to the linear function after multiple freezing-thawing of brine. Activity enhancement was achieved only in the brine devoid of lipids and suspension. Study results show also that measurement of lysosomal cathepsin D activity in the marinating brine requires also determining cathepsin E activity. Decreasing pore size of microfilter from 2.7 to 0.3 μm significantly reduced the lysosome content in the brine. The presence of lysosomes and the possibility of their separation as well as the likely release of cathepsins shall be considered during industrial application of the marinating brine, as new cathepsins preparations in fish and meat technology.