Mickelson M N
Appl Environ Microbiol. 1979 Nov;38(5):821-6. doi: 10.1128/aem.38.5.821-826.1979.
Antibacterial activity of lactoperoxidase (LP)-thiocyanate (SCN)-hydrogen peroxide (H2O2) on Streptococcus agalactiae requires that the three reactants must be in contact with the cells simultaneously. Small but assayable amounts of LP adsorb to the cell surface and are not removed by washing. A diffusible antibacterial product of LP-SCN-H2O2 reaction was not found under our experimental conditions. Incubation of S. agalactiae cells with LP-H2O2 and 14C-labeled sodium SCN resulted in the incorporation of SCN into the bacterial protein. Most of the LP-catalyzed, incorporated SCN was released from the bacterial protein. Most of the LP-catalyzed, incorporated SCN was released from the bacterial protein with dithiothreitol. Cells that had their membrane permeability changed by treatment with Cetab or 80% ethanol incorporated more SCN than did untreated cells, i.e., approximately 1 mol of SCN for each mol of sulfhydryl group present in the reaction mixture. Alteration of membrane permeability caused protein sulfhydryls, normally protected by the cytoplasmic membrane, to become exposed to oxidation. The results suggest the LP-H2O2-catalyzed incorporation of SCN into the proteins of S. agalactiae by a mechanism similar to that reported for bovine serum albumin. Removal of reactive protein sulfhydryls from a functional role in membrane transport and in glucolysis in a likely cause of the antibacterial effect for S. agalactiae.
乳过氧化物酶（LP）-硫氰酸盐（SCN）-过氧化氢（H₂O₂）对无乳链球菌的抗菌活性要求这三种反应物必须同时与细胞接触。少量但可检测的LP吸附到细胞表面，且洗涤后不会被去除。在我们的实验条件下未发现LP-SCN-H₂O₂反应的可扩散抗菌产物。用LP-H₂O₂和¹⁴C标记的硫氰酸钠孵育无乳链球菌细胞导致SCN掺入细菌蛋白质中。大部分由LP催化掺入的SCN从细菌蛋白质中释放出来。大部分由LP催化掺入的SCN用二硫苏糖醇从细菌蛋白质中释放出来。用西他氯铵或80%乙醇处理使膜通透性改变的细胞比未处理的细胞掺入更多的SCN，即反应混合物中每摩尔巯基大约掺入1摩尔SCN。膜通透性的改变使通常受细胞质膜保护的蛋白质巯基暴露于氧化作用。结果表明，LP-H₂O₂催化SCN通过一种类似于报道的牛血清白蛋白的机制掺入无乳链球菌的蛋白质中。从膜转运和糖酵解的功能作用中去除反应性蛋白质巯基可能是无乳链球菌抗菌作用的原因。
