Endoprotease and Exopeptidase Activities in the Hepatopancreas of the Cuttlefish Sepia officinalis, the Squid Todarodes pacificus, and the Octopus Octopus vulgaris Cuvier

This study examined and compared the exopeptidase and endoprotease activities of the hepatopancreas (HP) of cuttlefish, squid, and octopus species. The protein concentration in crude extract (CE) from octopus HP was 3,940 mg/100 g, lower than those in CEs from squid HP (4,157 mg/100 g) and cuttlefish HP (5,940 mg/100 g). With azocasein of pH 6 as a substrate, the total activity in HP CE of octopus was 31,000 U, lower than the values for cuttlefish (57,000 U) and squid (69,000 U). Regardless of sample type, the total activities of the CEs with azocasein as the substrate were higher at pH 6 (31,000-69,000 U) than at pH 9 (19,000-34,000 U). With L-leucine-p-nitroanilide (LeuPNA) of pH 6 as the substrate, the total activity of the HP CE from octopus was 138,000 U, higher than values from both cuttlefish HP (72,000 U) and squid HP (63,000 U). Regardless of sample type, the total activities of the CEs with LeuPNA as the substrate were higher at pH 6 (63,000-138,000 U) than at pH 9 (41,000-122,000 U). With LeuPNA as the substrate, the total activities of the CEs from octopus HP and cuttlefish HP were higher at pH 6 than at pH 9. However, there was no difference in total activity between pH 6 and 9 for squid HP CE with LeuPNA as the substrate. These results suggest that the octopus HP is superior to the cuttlefish HP and squid HP as a potential resource for extracting exopeptidases. Exopeptidases from octopus HP have potential industrial applications and their use might aid in reducing pollution related to the octopus industry.