Phospholipases

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Phospholipases are a group of enzymes that hydrolyze phospholipids into fatty acids and other lipophilic molecules. There are four major classes of phospholipases; phospholipase A (PLA) (E.C. 3.1.1.4), phospholipase B (E.C. 3.1.1.5), phosphoinositide-specific phospholipase C (PLC) (E.C. 3.1.4.11) and phospholipase D (PLD) (E.C. 3.1.4.50).

PLA is subdivided into PLA₁ which cleave phospholipids at the sn-1 ester bond and PLA₂, which cleave at the sn-2 bond. Their most common substrate is phosphatidylcholine, which generates lysophosphatidylcholine and arachidonic acid. PLA is regulated by phosphorylation and by intracellular Ca²⁺ concentrations. PLC is subdivided into β, γ, δ, ε, ζ and η subtypes, which catalyze the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP₂) to inositol 1,4,5-trisphosphate (IP₃) and 1,2-diacylglycerol (DAG). IP₃ and DAG both have important second messenger functions. PLC-β is primarily activated by G_q/11 proteins and PLC-γ is activated by phosphorylation in response to a variety of growth factor and immune system signals. PLD is subdivided into PLD1 and PLD2, and catalyzes the hydrolysis of phosphatidylcholine to phosphatidic acid and choline. PLD is regulated by several small GTPases, including ARF1 and RhoA, and protein kinase C-α.

Phospholipases are ubiquitously expressed and have diverse biological functions including roles in inflammation, cell growth, signaling and death, and maintenance of membrane phospholipids.

External Sources of Pharmacological Information for Phospholipases

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Phospholipase Gene Data