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EC number
CAS number 9016-18-6
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO

In enzymology, a carboxylesterase or carboxylic-ester hydrolase (EC is an enzyme that catalyzes a chemical reaction of the form

a carboxylic ester + H2O an alcohol + a carboxylate

Thus, the two substrates of this enzyme are carboxylic ester and H2O, whereas its two products are alcohol and carboxylate.[1]

Most enzymes from this group are serine hydrolases belonging to the superfamily of proteins with alpha/beta hydrolase fold. Some exceptions include an esterase with beta-lactamase like structure (PDB: 1ci8​).

Carboxylesterases are widely distributed in nature, and are common in mammalian liver. Many participate in phase I metabolism of xenobiotics such as toxins or drugs; the resulting carboxylates are then conjugated by other enzymes to increase solubility and eventually excreted.

The carboxylesterase family of evolutionarily related proteins (those with clear sequence homology to each other) includes a number of proteins with different substrate specificities, such as acetylcholinesterases.


The last enzyme also participates in alkaloid biosynthesis.


Humans genes that encode carboxylesterase enzymes include:

An approved nomenclature has been established for the five mammalian carboxylesterase gene families.[2]


  1. ^ Aranda, Juan; Cerqueira, N. M. F. S. A.; Fernandes, P.A.; Roca, M.; Tuñon, I.; Ramos, M. J. (2014). "The Catalytic Mechanism of Carboxylesterases. A Computational Study.". Biochemistry. 53 (36): 5820–5829. doi:10.1021/bi500934j. 
  2. ^ Holmes RS, Wright MW, Laulederkind SJ, Cox LA, Hosokawa M, Imai T, Ishibashi S, Lehner R, Miyazaki M, Perkins EJ, Potter PM, Redinbo MR, Robert J, Satoh T, Yamashita T, Yan B, Yokoi T, Zechner R, Maltais LJ (2010). "Recommended nomenclature for five mammalian carboxylesterase gene families: human, mouse, and rat genes and proteins". Mamm. Genome. 21 (9-10): 427–41. PMC 3127206Freely accessible. PMID 20931200. doi:10.1007/s00335-010-9284-4. 

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