Engineering increased stability in the antimicrobial peptide pediocin PA-1

Pediocin PA-I is a food grade antimicrobial peptide that has been used as a food preservative. Upon storage at 4 degreesC or room temperature, pedioci n PA-I looses activity, and there is a concomitant 16-Da increase in the mo lecular mass. It is shown that the loss of activity follows first-order kin etics and that the instability can be prevented by replacing the single met hionine residue (Met31) in pediocin PA-1. Replacing Met by Ala, lie, or Leu protected the peptide from oxidation and had only minor effects on bacteri ocin activity (for most indicator strains 100% activity was maintained). Re placement of Met by Asp was highly deleterious for bacteriocin activity.