Purification and Characterization of Aminopeptidase from Euphausia superba

Krill aminopeptidase was purified about, 1,100-fold from an extract of Euphausia superba with DEAE-cellulose column chromatography, Toyopearl HW55, and hydroxyapatite column chromatography. The final preparation was electrophoretically homogeneous. The molecular weight was determined to be 140,000 by gel filtration and SDS-polyacrylamide disc gel electrophoresis. The optimum pH and optimum temperature were 8.4 and 45°C respectively. Krill aminopeptidase was inhibited by EDTA, Hg^{+ +} and amastatin, and partially by bestatin, and was activated by Co ^{+ +}. Alanyl-p-nitroanilide was hydrolyzed faster than leucyl-p-nitroanilide. Alanyl peptides (di-, tri-, tetra- and hexa-alanyl peptide) were hydrolyzed very fast.

These results suggest that krill aminopeptidase is an alanine aminopeptidase which is activated by cobaltous ion.