TABLE 4

Bacterial acyl hydrolases that contribute to virulence

Enzyme typeExampleMass (kDa)Structural featuresEnzymatic activitySecretion typeDescribed role(s) in virulence
Outer membrane acyl hydrolases which adopt an antiparallel β-barrel structureHelicobacter pylori PldA1∼42Integral membrane antiparallel β-barrel; active site Ser144, His 142, and Asn146; Ca2+-dependent dimerization activates PLA activity (data derived from the E. coli homologue)PLASPa (data derived from E. coli homologue)Hemolytic activity (77)
Supports growth of bacteria at low pH (78)
Aids in colonization of gastric mucosa (77)
Induces MAPK activation (74)
Surface-associated PLA2Legionella pneumophila PlaB∼54Active site Ser in varied lipase motif THSTG includes Ser85, Asp203, and His251; oligomerization inactivates the enzymePLA and LPLALocated at bacterial surface but mode of secretion unknownHemolytic activity (85)
Required for replication in lungs and dissemination to spleen (86)
Modulates macrophage recruitment (86)
Acyl hydrolases from the SGNH esterase familySalmonella enterica serovar Typhimurium SseJ∼46Predicted SGNH esterase family; active site Ser151, Asp 247, His384; requires activation by eukaryotic cofactorsPLA and GCATaseInjected in host cell by Salmonella pathogenicity island 2 T3SSInteracts with RhoA GTPase in host cell, which triggers its GCATase activity (101, 102)
Destabilizes the phagosome membrane and thereby opposes activity of the effector SifA (96)
Required for intracellular replication (104)
Secreted acyl hydrolases which adopt the α/β hydrolase foldYersinia enterocolitica YplA∼53Predicted α/β hydrolase fold; active site Ser in GxSxG lipase motif; requires Ca2+PLA2Secreted by Ysc and Ysa type III, as well as flagellar secretion systemsParticipates in bacterial colonization (106)
Induces necrosis (106)
Secreted patatin-like acyl hydrolasesPseudomonas aeruginosa ExoU∼74Active site Ser in GxSxG lipase motif; requires activation by eukaryotic factorsPLA [substrates PC, PE, PA, PI(4,5)P2), LPLA]Injected in host cell by T3SSInteracts with ubiquitin or ubiquitinylated proteins in host cell, which triggers its catalytic activity (139)
Disrupts focal adhesion, inducing cytoskeletal collapse and membrane blebbing, which leads to plasma membrane disruption (150)
Alters signaling pathways: arachidonic acid-dependent inflamatory response, c-fos, c-jun, and NF-κB through PAF receptor (156159)
Cytotoxic to several cell types (135, 149, 152)
Class XIB PLA2sStreptococcus pyogenes SlaA∼21Highly conserved active site region (DXCCXXHDXCY) and Ca2+-binding loopPLA2Secreted, SPEnters epithelial cells in actin-dependent manner (178)
Cytotoxic (178)
  • a SP, predicted signal peptide.