Metabolism in marine flatfish--III. Measurement of elastase activity in the digestive tract of Dover sole (Solea solea L.).

A critical assessment of different methods for measuring elastase activity in crude preparations has been made using whole intestinal homogenates of Dover sole. The use of the natural substrate elastin or its dyed derivatives gave optimal pH values in the alkaline region (pH 9.4-9.8) whereas artificial substrates showed optimal hydrolysis nearer neutrality in the region pH 8.1-8.2. Exoproteases may interfere with certain assay procedures. The properties of Dover sole elastase have been further investigated using chromatographic techniques which indicated that the main elastase activity has a molecular weight of approximately 19,500 and an isoelectric point in the region of pH 5.7.