人ⅡA型磷脂酶A_2衍生肽P26抗菌作用与结构修饰的研究

目的比较人ⅡA型磷脂酶A2(phospholipase A2,PLA2)C末端衍生的多肽和经修饰后的环肽对不同细菌在体外的杀菌效应,了解其作用机制。方法根据人ⅡA型PLA2氨基酸顺序C末端26个氨基酸残基,合成直链肽P26,同时将其修饰为环肽P26。采用琼脂铺板计数法,将不同浓度的两种多肽分别与6种细菌在37℃孵育2 h,然后铺板并置于37℃恒温箱培养18～24 h,记录每一琼脂板上的菌落数(CFU),并计算多肽作用后的杀菌率。结果两种多肽对革兰阳性菌金黄色葡萄球菌、枯草杆菌和炭疽杆菌有较强的杀菌活性,环肽P26的作用比直链肽P26强4倍左右;对革兰阴性菌大肠杆菌、变形杆菌和绿脓杆菌的杀菌作用较弱,而环肽P26的作用更弱。结论衍生自人ⅡA型PLA2 C末端26个氨基酸残基的肽P26和修饰得到的环肽P26对G+菌有较强的杀菌活性,经修饰成环肽后作用更强,可能与环肽分子带的正电荷更集中有关。

Bactericidal activity and structure modification of the polypeptide P26

Aim To study the bactericidal activity and structure modification of the polypeptide P26 which derives from C-terminal 26 amino acid residues of Human Group ⅡA phospholipase A2(Group IIA PLA2) in vitro,and to understand the mechanism of bactericidal activity for the two derived peptides.Methods Linear polypeptide P26 was synthesized acorrding to the C-terminal 26 amino acid residues sequence of Human Group ⅡA phospholipase A2,and some of them were modified to be a cyclic polypeptide P26.6 species of bacterial solution with different concentration of polypeptide were incubated at 37℃ for 2 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 unit was counted and the bactericidal rates were calculated.Results The two polypeptides possessed potent bactericidal activity on the gram-positive(G+)bacteria,such as Staphylococcus aureus,Bacillus subtilis,Bacillus anthrax;but weak bactericidal activity on the gram-negative(G-)bacteria,such as Escherichia coli,Bacillus proteus,Bacillus pyocyaneus.The bactericidal activity of the cyclic polypeptide was abou 4 times higher than linear polypeptide P26 on the G+bacteria,but it was not for the G-bacteria.Conclusions The two peptides which derive from Cterminal 26 amino acid residues of Human GroupⅡA phospholipase A2 possess potent bactericidal activity against G+bacteria.The activity of cylic P26 is higher than linear P26 on G+bacteria.It may be due to the more concentrated charged residues in cyclic P26.