Identification of neutral aminopeptidases responsible for peptidolysis in postmortem rabbit skeletal muscle.

Abstract

A survey of the total aminopeptidase activity of rabbit skeletal muscle at neutral pH values was performed, using the 2-naphthylamide derivatives of nine amino acids (Ala, Glu, Gly, Leu, Lys, Met, Pro, Ser and Val) as substrates. DEAE-cellulose column chromatography of the muscle extract revealed five major activity peaks that were eluted at 0, 0.03, 0.09, 0.11 and 0.18 m NaCl. The eluates around 0.18 m NaCl showed high activity against all substrates and contained the major aminopeptidases. These aminopeptidases were the 160,000-dalton aminopeptidase (aminopeptidase C) and hydrolase H purified from rabbit skeletal muscle. The values of substrate specificity were fairly compatible with the pattern of free amino acids increasing during the storage of rabbit muscle, indicating that these enzymes are responsible for the increment of free amino acids during aging of rabbit muscle.