The Phospholipases

Phospholipases are a class of ubiquitous enzymes that have in common their substrate and the fact that they are all esterases. Beyond that, they are a diverse group of enzymes that fall into two broad categories, the acyl hydro lases and the phosphodiesterases. The former group is made up of the phos pholipases Al and A , phospholipase B, and the lysophospholipases. On the 2 other hand, the phosphodiesterases are the phospholipases C and D. The scheme indicates the site of attack of each type of phospholipase. PLA 1 PLB~j ft 0\ ~-C-O-C-R d ~ 2 I 1 R-C-0-C-H 0 2 /H2-6-0-U-0-x PLA, ~ 6- '" PLC PLD The lysophospholipases, not shown, have in some cases properties similar to phospholipase B and are known to attack the acyl ester at either position 1 or position 2 of the glycerol backbone. Furthermore, some of the phos pholipases C and D do not hydrolyze phosphoglycerides but use sphingo myelinase as their substrate. These phospholipases C are also referred to as sphingomyelinases. The products of that reaction are phosphocholine plus ceramide.

Contenu
1 Assay of Phospholipases.- 1.1. General Considerations and Choice of Assay.- 1.2. Methods of Assay.- 2 Bacterial Acyl Hydrolases (Phospholipases A, B, and Lysophospholipases).- 2.1. General Considerations.- 3 Bacterial Phosphodiesterases (Phospholipases C and D).- 3.1. General Considerations.- 3.2. Bacterial Phospholipases D.- 3.3. Summary.- 4 Other Microorganisms.- 4.1. General Comments.- 4.2. Penicillium notatum.- 4.3. Saccharomyces cerevisiae.- 4.4. Amoebic Phospholipases.- 4.5. Tetrahymena pyriformis.- 5 Plant Phospholipases.- 5.1. General Considerations.- 5.2. Initial Studies.- 5.3. Purification of Phospholipase D.- 5.4. Transphosphatidylation and Substrate Specificity.- 5.5. Factors Regulating Phospholipase D Action.- 5.6. Function of Plant Phospholipases D.- 6 Cellular Phospholipases Al and Lysophospholipases of Mammals.- 6.1. General Introduction to Cellular Phospholipases from Mammals.- 6.2. Phospholipase A1: General Considerations.- 6.3. Lysophospholipases: General Considerations.- 7 Phospholipase A2 of Mammalian Cells.- 7.1. General Considerations.- 7.2. Phospholipase A2 of Neutrophils (Polymorphonuclear Leukocytes).- 7.3. Phospholipase A2 of Brain.- 7.4. Phospholipase A2 of Platelet.- 7.5. Phospholipase A2 of Macrophages.- 7.6. Phospholipase A2 of Erythrocytes.- 7.7. Phospholipase A2 of Liver Mitochondria.- 7.8. Phospholipase A2 of Lung Exudate.- 7.9. Phospholipases A2 in Cultured Tumor Cells.- 7.10. Intestinal Phospholipase A2.- 7.11. Heart Phospholipase A2.- 7.12. Spleen Phospholipase A2.- 8 Phospholipases C and Phospholipases D of Mammalian Cells.- 8.1. General Considerations.- 8.2. Mammalian Phospholipases C: Historical Background.- 8.3. Sphingomyelinases.- 8.4. Phospholipase D.- 8.5. Summary.- 9 Pancreatic and Snake Venom Phospholipases A2.- 9.1. General Considerations.- 9.2. Purification, Activation, and Some Characteristics of the Pancreatic Phospholipase A2.- 9.3. Snake Venom Phospholipases A2.- 9.4. Structure of the Phospholipases A2.- 9.5. Functionality of Amino Acids in Venom and Pancreatic Phospholipases A2: Enzyme Modification.- 10 Mechanism of Phospholipase A2 Action.- 10.1. General Considerations.- 10.2. Metal Ion Binding to the Enzyme.- 10.3. Phospholipase Substrate Binding.- 10.4 Mechanism of Phospolipase A2 Hydrolysis.- 11 Function of Phospholipases.- 11.1. General Considerations.- 11.2. The Phosphatidylinositol (PI) Cycle and the Arachidonate Cascade.- 11.3. Phospholipases in Digestion of Dietary Fat.- 11.4. Phospholipases in Lipoprotein Metabolism.- 11.5. Action of Snake-Venom Enzymes.- 11.6. Phospholipases as Structural Probes.- 11.7. Summary.- References.