PURIFICATION AND CHARACTERIZATION OF AEROMONAS-CAVIAE AMINOPEPTIDASE POSSESSING DEBITTERING ACTIVITY

An aminopeptidase (EC 3.4.11.10) was purified to homogeneity from the culture filtrate of Aeromonas caviae T-64. The purified enzyme showed maximum activity at pH 8.5 and 50 degrees C and was inhibited by o-phe nanthroline and EDTA. The M-r values estimated by MALDI-TOF mass spect rometry and SDS-PAGE were 29 500 and 31 000 Da, respectively. These re sults indicate that the enzyme is a monomeric metalloenzyme. The enzym e hydrolyzed the di-and tripeptides containing hydrophobic amino acid residues such as valine, isoleucine, leucine, tyrosine, and phenylalan ine in the N-terminal and/or adjacent positions with high hydrolysis e fficiency (K-cat/K-m). This substrate specificity was not restricted t o the di-and tripeptides as the peptides longer than tripeptides were hydrolyzed at a high rate when hydrophobic amino acid residues were lo cated in the N-terminal region.