内科

目的探讨人ⅠB型磷脂酶A2（groupⅠB phospholipase A2, PLA2ⅠB）N末端衍生12肽的结构与杀菌活性的关系。方法以人PLA2ⅠB一级结构N末端的12个氨基酸残基为模板，分别合成结构不同的多肽，采用琼脂铺板计数法，记录并计算不同浓度（1000、200、40、8 μg/mL）的多肽对革兰阳性（G+）菌（金黄色葡萄球菌）和革兰阴性（G-）菌（大肠埃希菌）的杀菌率。结果PLA2-Q4D、PLA2-C11R抗菌活性明显降低。第4位中性氨基酸Q替换为酸性氨基酸后（PLA2-Q4D），失去了杀G-菌的作用，杀G+菌的活性也明显降低；第11位C替换为精氨酸后（PLA2-C11R）也明显失去了杀G-菌的作用，杀G+菌的活性也明显降低。结论人PLA2ⅠB衍生肽PLA2的杀菌作用与其疏水性氨基酸的比例和位置有关，也与碱性氨基酸的量和位置有关，在特定位置改变疏水性氨基酸可降低它的杀菌活性，增加碱性氨基酸的量不一定能提高它的杀菌活性。

ObjectiveTo study the relationship between structure and bactericidal activity of the polypeptides derived from the C-terminal human Group ⅠB Phospholipase A2（PLA2 ⅠB）. MethodsAccording to the 12 amino acid residues of the N-terminal of human PLA2 ⅠB, polypeptides of different structures were synthesized.Bactericidal rate of different concentrations of polypeptides (1000, 200, 40 and 8μg / ml) to Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) were recorded and counted by agar plate counting method. ResultsThe activities of PLA2-Q4D and PLA2-C11R were significantly decreased after the structure was changed. After the fourth neutral amino acid Q replaced by acidic amino acids (PLA2-Q4D), it lost the role of killing G- bacteria, and the activity of killing G+ bacteria was also significantly decreased; the 11th C substitution of R also significantly lost the bactericidal activity to G- bacteria , killing G+ bacteria activity was significantly decreased. ConclusionsThe bactericidal activity of human PLA2ⅠB derivative peptide PLA2 is related to the ratio of hydrophobicity, the amount of basic amino acids and the position of the amino acids. Changing the hydrophobicity in specific position can reduce its bactericidal activity, increasing the amount of basic amino acid does not necessarily improve its bactericidal activity.