Aminopeptidase from jumbo squid ( Dosidicus gigas) hepatopancreas: purification, characterisation, and casein hydrolysis.

An aminopeptidase (AP) was partially purified from jumbo squid ( Dosidicus gigas) hepatopancreas with 154.24-fold and yield of 6.15%. The purification procedure consisted of ammonium sulphate fractionation and DEAE-Sephacel chromatography. The enzyme was approximately 48–53 kDa as estimated by SDS-PAGE. Withl-leu- p-NA, it had optimum activity at pH 8.0 and 30 °C. The Km and Vmax/ Km values of the enzymes forl-leu- p-NA were 0.326 mm and 2787 at 37 °C, respectively. Activation energy ( Ea) of the enzyme was 53.50 kJ M−1.The AP showed activity against seven synthetic substrates:l-proline>l-methionine>Ac.l-γ-glutamic>l-glycine>l-leucine>l-alanine>l-lysine- p-NA. The enzyme was strongly inhibited by Bestatin, partially inhibited by a metal-chelating agent and by PCMB, a cystein protease inhibitor. Zn2+ and (or) Ca2+ seemed to be its metal cofactor(s). Incubation of casein with the partially purified AP resulted in a degree of hydrolysis of 6%. [ABSTRACT FROM AUTHOR]