5.3.3.2	-15°C, stable for several months	
5.3.3.2	-20°C, 0.1 M potassium phosphate buffer, pH 7.0, 2 mM dithiothreitol, stable for several weeks	
5.3.3.2	-80°C, 0.05 M Tris/HCl, pH 7.5, containing 0.01 mM leupeptin, 2 mM dithiothreitol, 5% glycerol, 55% of the activity is recovered after 3 months