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, distinguished by the type of reaction which they catalyze:

• Phospholipase A
  • Phospholipase A1 - cleaves the SN-1 acyl chain.
  • 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.  Phospholipase Cs 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.