Bacterial phospholipases C.
A variety of pathogenic bacteria produce phospholipases C, and since the discovery in 1944 that a bacterial toxin (Clostridium perfringens alpha-toxin) possessed an enzymatic activity, there has been considerable interest in this class of proteins. Initial speculation that all phospholipases C would have lethal properties has not been substantiated. Most of the characterized enzymes fall into one of four groups of structurally related proteins: the zinc-metallophospholipases C, the sphingomyelinases, the phosphatidylinositol-hydrolyzing enzymes, and the pseudomonad phospholipases C. The zinc-metallophospholipases C have been most intensively studied, and lethal toxins within this group possess an additional domain. The toxic phospholipases C can interact with eukaryotic cell membranes and hydrolyze phosphatidylcholine and sphingomyelin, leading to cell lysis. However, measurement of the cytolytic potential or lethality of phospholipases C may not accurately indicate their roles in the pathogenesis of disease. Subcytolytic concentrations of phospholipase C can perturb host cells by activating the arachidonic acid cascade or protein kinase C. Nonlethal phospholipases C, such as the Listeria monocytogenes PLC-A, appear to enhance the release of the organism from the host cell phagosome. Since some phospholipases C play important roles in the pathogenesis of disease, they could form components of vaccines. A greater understanding of the modes of action and structure-function relationships of phospholipases C will facilitate the interpretation of studies in which these enzymes are used as membrane probes and will enhance the use of these proteins as models for eukaryotic phospholipases C.
Titball
R W
RW
Chemical and Biological Defence Establishment, Porton Down, Salisbury, United Kingdom.
D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D001424:Bacterial Infections / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008969:Molecular Sequence Data; D010743:Phospholipids / Q000378:metabolism; D010738:Type C Phospholipases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D014774:Virulence
D010743:Phospholipids; D010738:Type C Phospholipases