Studies on the protease activities in Norway lobster (Nephrops norvegicus) and their role in the phenolase activation process

Proteolytic activity in Norway lobster (Nephrops norvegicus) was studied. Three proteases were separated and partially purified from Norway lobster heads by a combination of acetone precipitation and DEAE-Sepharose CL-6B column chromatography and designated as enzymes I, II and III. Enzyme III had a pH optimum at around 8.2 towards casein as substrate. Enzymes I and II were found to be very similar in most aspects; they showed multiple pH optima towards casein. Studies on sensitivity to different inhibitors suggested that enzymes I and II were likely to be thiol proteases and enzyme III a metal-dependent serine protease. It was found that only enzyme III was involved in the phenolase activation process in Norway lobster.