Phospholipase A2

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Phospholipases A2 (PLA2s) EC 3.1.1.4 are enzymes that specifically hydrolyze the sn-2 fatty acid acyl bond of phospholipids, producing a free fatty acid and a lyso-phospholipid. A large range of fatty acids can be bound to the sn2 position of phospholipids, including arachidonic acid and eicosapentaenoic acid.

Bee venom phospholipase A2 sPLA2. Middle plane of the lipid bilayer - black dots. Boundary of the hydrocarbon core region - red dots (extracellular side). Layer of lipid phosphates - yellow dots.

1 Families
2 References
3 Genes
4 External links

[edit] Families

Phospholipases A2 include several unrelated protein families with common enzymatic activity. Two most notable families are secreted and cytosolic phospholipases A2.

[edit] Secreted phospholipases A2 (sPLA2)

The extracellular forms of phospholipases A2 have been isolated from different venoms (snake, bee, and wasp), from virtually every studied mammalian tissue (including pancreas and kidney) as well as from bacteria. They require Ca²⁺ for activity.

Pancreatic PLA2 serve for the initial digestion of phospholipid compounds in dietary fat. Venom phospholipases help to immobilize prey by promoting cell lysis.

[edit] Cytosolic phospholipases A2 (cPLA2)

The intracellular PLA2 are also Ca-dependent, but they have completely different 3D structure and significantly larger than sectreted PLA2 (more than 700 residues). They include C2 domain and large catalytic domain.

These phospholipases are involved in cell signaling processes, such as inflammatory response. The produced Arachidonic acid is both a signaling molecule and the precursor for other signalling molecules termed eicosanoids. These include leukotrienes and prostaglandins. Some eicosanoids are synthesized from diacylglycerol, released from the lipid bilayer by phospholipase C (see below).

Phospholipases A2 can be classified based on sequence homology.^[1]

[edit] Outer membrane phospholipase A (OMPLA)

Outer membrane phospholipase A is an integral membrane phospholipase of Gram-negative bacteria. It has a broad substrate specificity. In Escherichia coli it participates in the secretion of bacteriocins. The accumulation of lysophospholipids and free fatty acids in the outer membrane enhance the permeability of the outer membrane. This facilitates the secretion of bacteriocins.

[edit] References

^ Six DA, Dennis EA. The expanding superfamily of phospholipase A(2) enzymes: classification and characterization. Biochimica et Biophysica Acta. 2000;1488(1-2):1-19