phospholipase

thumb|right|Phospholipase cleavage sites. An enzyme that displays both PLA1 and PLA2 activities is called a phospholipase B.

A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances. There are four major classes, termed A, B, C, and D, which are distinguished by the type of reaction which they catalyze: Phospholipase A Phospholipase A1 – cleaves the sn-1 acyl chain (where sn refers to stereospecific numbering). Phospholipase A2 – cleaves the sn-2 acyl chain, releasing arachidonic acid. Phospholipase B – cleaves both sn-1 and sn-2 acyl chains; this enzyme is also known as a lysophospholipase. Phospholipase C – cleaves before the phosphate, releasing diacylglycerol and a phosphate-containing head group. PLCs play a central role in signal transduction, releasing the second messenger inositol triphosphate. Phospholipase D – cleaves after the phosphate, releasing phosphatidic acid and an alcohol.