Quorum sensing is a regulatory system used by bacteria for controlling gene expression in response to increasing cell density. This regulatory process manifests itself with a variety of phenotypes including biofilm formation and virulence factor production. Coordinated gene expression is achieved by the production, release, and detection of small diffusible signal molecules called autoinducers. The N-acylated homoserine lactones (AHLs) comprise one such class of autoinducers, each of which generally consists of a fatty acid coupled with homoserine lactone (HSL). Regulation of bacterial quorum sensing signaling systems to inhibit pathogenesis represents a new approach to antimicrobial therapy in the treatment of infectious diseases. AHLs vary in acyl group length (C4-C18), in the substitution of C3 (hydrogen, hydroxyl, or oxo group), and in the presence or absence of one or more carbon-carbon double bonds in the fatty acid chain. These differences confer signal specificity through the affinity of transcriptional regulators of the LuxR family. C18-HSL is one of four lipophilic, long acyl side-chain bearing AHLs produced by the LuxI AHL synthase homolog SinI involved in quorum sensing signaling in strains of S. meliloti, a nitrogen-fixing bacterial symbiont of the legume M. sativa. C18-HSL and other hydrophobic AHLs tend to localize in relatively lipophilic cellular environments of bacteria and cannot diffuse freely through the cell membrane. The long-chain N-acylhomoserine lactones may be exported from cells by efflux pumps or may be transported between communicating cells by way of extracellular outer membrane vesicles.
Myeloperoxidase, human white blood cells (MPO) 是一种过氧化物酶,通过促进活性氧 (ROS) 和活性氮 (RNS) 的生成来调节小胶质细胞及中性粒细胞的极化,并影响炎症相关信号通路,进而介导氧化应激。此外,Myeloperoxidase, human white blood cells 还具备抗菌 (antibacterial) 活性。