Purification and Characterization of Aminopeptidase Fractions From Squid (Illex Illecebrosus) Hepatopancreas

Atlantic short finned squid hepatopancreas (HP) aminopeptidases (APs) were partially separated from endoproteinases to determine their usefulness in accelerating Cheddar cheese ripening. Squid HP endoproteinases were predominantly cysteine proteases. The main peptidases identified in squid HP were APs. Several of the APs identified were metalloproteases and were activated by Ca2+, Mn2+, Zn2+ or Mg2+ salts. Squid HP homogenate was held at pH 7 at OC for 20 h, incubated with 5 mM ZnSO4, fractionated by ammonium sulfate (20–80%) and dialyzed against 25 mM ZnSO4. The procedure resulted in a 3–186 fold increase in the ratio of exopeptidase to endoproteinase activity with different AP substrates. Recovery of specific APs ranged between 14–47%. The partially purified squid HP peptidases had a higher ratio of exopeptidase to endoproteinase activity than two commercial products with AP activity, Flavozyme and Neutrase.