In biochemistry, an esterase is a class of enzyme that splits esters into an acid and an alcohol in a chemical reaction with water called hydrolysis (and as such, it is a type of hydrolase).

A wide range of different esterases exist that differ in their substrate specificity, their protein structure, and their biological function.

• EC 3.1.1: Carboxylic ester hydrolases
  • Acetylesterase (EC 3.1.1.6), splits off acetyl groups
    • Cholinesterase
      • Acetylcholinesterase, inactivates the neurotransmitter acetylcholine
      • Pseudocholinesterase, broad substrate specificity, found in the blood plasma and in the liver
  • Pectinesterase (EC 3.1.1.11), clarifies fruit juices
• EC 3.1.2: Thiolester hydrolases
  • Thioesterase
    • Ubiquitin carboxy-terminal hydrolase L1
• EC 3.1.3: Phosphoric monoester hydrolases
  • Phosphatase (EC 3.1.3.x), hydrolyses phosphoric acid monoesters into a phosphate ion and an alcohol
    • Alkaline phosphatase, removes phosphate groups from many types of molecules, including nucleotides, proteins, and alkaloids.
    • Phosphodiesterase (PDE), inactivates the second messenger cAMP
      • cGMP specific phosphodiesterase type 5, is inhibited by Sildenafil (Viagra)
  • Fructose bisphosphatase (3.1.3.11), converts fructose-1,6-bisphosphate to fructose-6-phosphate in gluconeogenesis
• EC 3.1.4: Phosphoric diester hydrolases
• EC 3.1.5: Triphosphoric monoester hydrolases
• EC 3.1.6: Sulfuric ester hydrolases (sulfatases)
• EC 3.1.7: Diphosphoric monoester hydrolases
• EC 3.1.8: Phosphoric triester hydrolases
• Exonucleases (deoxyribonucleases and ribonucleases)
  • EC 3.1.11: Exodeoxyribonucleases producing 5'-phosphomonoesters
  • EC 3.1.13: Exoribonucleases producing 5'-phosphomonoesters
  • EC 3.1.14: Exoribonucleases producing 3'-phosphomonoesters
  • EC 3.1.15: Exonucleases active with either ribo- or deoxy-
• Endonucleases (deoxyribonucleases and ribonucleases)
  • Endodeoxyribonuclease
  • Endoribonuclease
  • either deoxy- or ribo-

• Enzyme
• List of enzymes
• Carboxylic acid
• Ester
• Leukocyte esterase
• Hemagglutinin esterase
• Nuclease
• Lipase
• Asymmetric ester hydrolysis with pig-liver esterase

• Enzyme nomenclature