Study on Bactericidal Activity of the Polypeptide M17 Derived from Human Group ⅡA Phospholipase A2

Abstract:

Objective: To study and compare the bactericidal activity of the polypeptide M17, P26 and N_1-11 which derives from hunman group ⅡA phospholipase A₂ (PLA₂, phospholipase A₂) in vitro. Method: Peptide M 17(p_51-67), P26 (p_99-124), N_{1– 11} (p_1-11) were synthesized according to the sequence of human GroupⅡA PLA₂ amino acid. Six species of bacterial, Gram positive(G⁺) Staphy 1ococcus aureus, Bacillus subtilis, Enterococcus faecium, Gram negative(G^-) Escherichia coli , Acinetobacter baumannii, Bacillus pyocyaneus , were incubated with different concentration of polypeptides at 37℃ for 2.5 hours in a water bath respectively. Then the reaction solution was diluted and agar plates were poured. After 18-24 hours incubation in the thermostated container at 37℃.The colony formed units were counted and the bactericida1 rates were calculated. Result: Regression equation of PLA₂M17 bactericidal activity on the G⁺ bacteria(lococcus aureus, Bacillus subtilis, Enterococcus faecium) were Y=1.464X+3.795(ED₅₀ 6.65 mg·L^-1),Y=1.152X+3.419(ED₅₀ 23.57 mg·L^-1), Y=0.836X+3.832 (ED₅₀ 24.95 mg·L^-1). Regression equation of M17 bactericidal activity on the G^-bacteria (E. coli , A. baumannii, B. pyocyaneus)were Y=0.877X+4.054(ED₅₀ 12.00 mg·L^-1),Y=1.094X+3.371(ED₅₀ 30.83 mg·L^-1),Y=1.027X+3.626(ED₅₀ 21.77 mg·L^-1). PLA₂M17 possessed potent bactericidal activity on the G⁺ bacteria and G^-bacteria.Regression equation of N_1-11 and P26 bactericidal activity on B. subtilis were Y=0.915X+2.766(ED₅₀ 276.39 mg·L^-1),Y=1.389X+1.668(ED₅₀ 250.52 mg·L^-1). Regression equation of N_1-11 and P26 bactericidal activity on E. coli were Y=1.327X+1.437(ED₅₀ 484.18 mg·L^-1), Y=0.881X+2.903(ED₅₀ 240.02 mg·L^-1).N_1-11 and P26 possessed strong bactericidal activity of G⁺ bacteria, but weaker activity of G^- bacteria. M17 possessed stronger bactericidal activity than N_1-11 and P26 on B. subtilis and E. coli. Conclusion: Peptide M17 derived from human Ⅱ type A PLA₂ highly conserve region possesses a strong bactericidal activity, this may be related to the M17 peptide molecules more easily binding to bacteria.