Department of Biochemistry and Immunology, FMRP-USP, Universidade de São Paulo, Brazil.
Biochimie. 2012 Jun;94(6):1437-40. doi: 10.1016/j.biochi.2012.03.020. Epub 2012 Apr 2.
The Human Secreted Group IID Phospholipase A(2) (hsPLA2GIID) may be involved in the human acute immune response. Here we have demonstrated that the hsPLA2GIID presents bactericidal and Ca(2+)-independent liposome membrane-damaging activities and we have compared these effects with the catalytic activity of active-site mutants of the protein. All mutants showed reduced hydrolytic activity against DOPC:DOPG liposome membranes, however bactericidal effects against Escherichia coli and Micrococcus luteus were less affected, with the D49K mutant retaining 30% killing of the Gram-negative bacteria at a concentration of 10μg/mL despite the absence of catalytic activity. The H48Q mutant maintained Ca(2+)-independent membrane-damaging activity whereas the G30S and D49K mutants were approximately 50% of the wild-type protein, demonstrating that phospholipid bilayer permeabilization by the hsPLA2GIID is independent of catalytic activity. We suggest that this Ca(2+)-independent damaging activity may play a role in the bactericidal function of the protein.
人分泌的 II 组磷酯酶 A(2)（hsPLA2GIID）可能参与了人体的急性免疫反应。在这里，我们已经证明了 hsPLA2GIID 具有杀菌和 Ca(2+)-非依赖性的脂质体膜损伤活性，并且我们将这些效应与该蛋白的活性位点突变体的催化活性进行了比较。所有突变体对 DOPC:DOPG 脂质体膜的水解活性降低，但对大肠埃希氏菌和藤黄微球菌的杀菌作用影响较小，D49K 突变体在 10μg/mL 浓度下仍保留 30%的革兰氏阴性菌杀伤作用，尽管没有催化活性。H48Q 突变体保持了 Ca(2+)-非依赖性的膜损伤活性，而 G30S 和 D49K 突变体约为野生型蛋白的 50%，表明 hsPLA2GIID 通过磷脂双层的渗透与催化活性无关。我们认为这种 Ca(2+)-非依赖性的损伤活性可能在该蛋白的杀菌功能中发挥作用。
