A STUDY OF THE SUBSTRATE-SPECIFICITY OF AMINOPEPTIDASE-N FROM LACTOCOCCUS-LACTIS SUBSP CREMORIS WG2

A systematic study was made of the ability of aminopeptidase N from La ctococcus lactis subsp, cremoris Wg2 to hydrolyse different peptide su bstrates. The enzyme showed a marked preference for substrates contain ing arginine as the N-terminal residue but, to a lesser extent, was al so capable of cleaving other residues such as lysine and leucine. Ther e was a tendency for the activity to increase with the hydrophobicity index of the C-terminal residue of dipeptide substrates. It was also o bserved that the enzyme tended to have higher affinities but lower V-m ax values for tripeptides with hydrophobic C-terminal residues. The va lues determined for K-m and V-max increased with chain length for olig opeptides of the general formula Lys-Phe-(Gly)(n), the optimum, as det ermined from V-max/K-m, being when n = 3. Typical K-m values for the m ost effective substrates were in the range 0.2-0.6 mM.