Kukkonen Maini, Korhonen Timo K
General Microbiology, Faculty of Biosciences, University of Helsinki, P.O. Box 56 (Viikinkaari 9), FIN-00014 Helsinki, Finland.
Int J Med Microbiol. 2004 Jul;294(1):7-14. doi: 10.1016/j.ijmm.2004.01.003.
The omptins are a family of enterobacterial surface proteases/adhesins that share high sequence identity and a conserved beta-barrel fold in the outer membrane. The omptins are multifunctional, and the individual omptins exhibit differing virulence-associated functions. The Pla plasminogen activator of Yersinia pestis contributes by several mechanisms to bacterial invasiveness and the systemic, uncontrolled proteolysis in plague. Pla proteolytically activates the human proenzyme plasminogen and inactivates the antiprotease alpha2-antiplasmin, and its binding to laminin localizes the uncontrolled plasmin activity onto basement membranes. These properties enhance bacterial migration through tissue barriers. Pla also degrades circulating complement proteins and functions in bacterial invasion into human epithelial cells. PgtE of Salmonella enterica and OmpT of Escherichia coli have been shown to degrade cationic antimicrobial peptides from epithelial cells or macrophages. PgtE and SopA of Shigella flexneri appear important in the intracellular phases of salmonellosis and shigellosis, whereas functions of OmpT have mainly been associated with protein degradation in E. coli cells. The differing virulence roles and functions have been attributed to minor sequence variations at the surface-exposed regions important for substrate recognition, to the dependence of omptin functions on lipopolysaccharide, and to the different regulation of omptin expression.
外膜蛋白酶是一类肠道细菌表面蛋白酶/黏附素，它们在外膜中具有高度的序列同一性和保守的β桶状折叠结构。外膜蛋白酶具有多种功能，不同的外膜蛋白酶表现出不同的与毒力相关的功能。鼠疫耶尔森菌的Pla纤溶酶原激活剂通过多种机制促进细菌的侵袭性以及鼠疫中的全身性、不受控制的蛋白水解。Pla通过蛋白水解作用激活人纤溶酶原酶原并使抗蛋白酶α2-抗纤溶酶失活，其与层粘连蛋白的结合将不受控制的纤溶酶活性定位于基底膜上。这些特性增强了细菌通过组织屏障的迁移能力。Pla还能降解循环中的补体蛋白，并在细菌侵入人上皮细胞中发挥作用。肠炎沙门氏菌的PgtE和大肠杆菌的OmpT已被证明能降解上皮细胞或巨噬细胞产生的阳离子抗菌肽。福氏志贺氏菌的PgtE和SopA在沙门氏菌病和志贺氏菌病的细胞内阶段似乎很重要，而OmpT的功能主要与大肠杆菌细胞中的蛋白质降解有关。不同的毒力作用和功能归因于对底物识别很重要的表面暴露区域的微小序列变异、外膜蛋白酶功能对脂多糖的依赖性以及外膜蛋白酶表达的不同调控。
