Biochemical Properties of a New Lantibiotic Produced by Lactococcus Zactis IO-1

A new peptide antibiotic was isolated from the culture broth of Lactococcus lactis IO-1 and biochemical properties of this compound were investigated. The peptide had a strong inhibitory effect on the growth of Bacillus subtilis Cl and the antibacterial spectrum and minimum inhibitory concentration (MIC) for various type strains showed that this antibiotic resembled nisin. Automated Edman degradation indicated the N-terminal amino acid of this peptide was isoleucine, the N-terminal amino acid for nisin. ‘H NMR spectra showed the presence of DHB,. However, hydrolysis using carboxypeptidase Y released isoleucine as the C-terminal amino acid which is not the C-terminal amino acid for nisin. The molecular weight of the IO-1 peptide is smaller than nisin and the amino acid composition was slightly different. The IO-1 peptide did not contain His and Ser and the Ile, Lys and Met content was less than that in nisin; these amino acids are the members of the C-terminal amino acid sequence of the nisin peptide. Thus, the peptide produced by strain IO-1 was a new lantibiotic with a different amino acid sequence from that of nisin