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The enzyme carboxylesterase (or carboxylic-ester hydrolase, EC 3.1.1.1; systematic name carboxylic-ester hydrolase) catalyzes reactions of the following form:

a carboxylic ester + H₂O ${\displaystyle \rightleftharpoons }$ an alcohol + a carboxylate

Most enzymes from this group are serine hydrolases belonging to the superfamily of proteins with α/β hydrolase fold. Some exceptions include an esterase with β-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 essential polyunsaturated fatty acid arachidonic acid (AA C₂₀H₃₂O₂; 20:4, n-6), formed by the synthesis from dietary linoleic acid (LA: C₁₈H₃₂O₂ 18:2, n-6), has a role as a human carboxylesterase inhibitor.

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.

Examples

• acetylcholinesterase
• ali-esterase,
• B-esterase,
• butyrate esterase,
• butyryl esterase,
• carboxylesterase 1
• carboxylesterase 2
• carboxylesterase 3
• esterase A,
• esterase B,
• esterase D,
• methylbutyrase,
• methylbutyrate esterase,
• monobutyrase,
• procaine esterase,
• propionyl esterase,
• triacetin esterase,
• vitamin A esterase, and
• cocaine esterase

The last enzyme also participates in alkaloid biosynthesis.

Genes

Humans genes that encode carboxylesterase enzymes include:

• CES1
• CES2
• CES3
• CES4
• CES7
• CES8

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

References

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. PMID 25101647.
2. PubChem. "Arachidonic acid". pubchem.ncbi.nlm.nih.gov. Retrieved 2022-11-24.
3. 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. doi:10.1007/s00335-010-9284-4. PMC 3127206. PMID 20931200.

Further reading

• Augusteyn RC, de Jersey J, Webb EC, Zerner B (1969). "On the homology of the active-site peptides of liver carboxylesterases". Biochim. Biophys. Acta. 171 (1): 128–37. doi:10.1016/0005-2744(69)90112-0. PMID 4884138.
• Barker DL, Jencks WP (1969). "Pig liver esterase. Physical properties". Biochemistry. 8 (10): 3879–89. doi:10.1021/bi00838a001. PMID 4981346.
• Bertram J, Krisch K (1969). "Hydrolysis of vitamin A acetate by unspecific carboxylesterases from liver and kidney". Eur. J. Biochem. 11 (1): 122–6. doi:10.1111/j.1432-1033.1969.tb00748.x. PMID 5353595.
• BURCH J (1954). "The purification and properties of horse liver esterase". Biochem. J. 58 (3): 415–26. doi:10.1042/bj0580415. PMC 1269916. PMID 13208632.
• Horgan DJ, Stoops JK, Webb EC, Zerner B (1969). "Carboxylesterases (EC 3.1.1). A large-scale purification of pig liver carboxylesterase". Biochemistry. 8 (5): 2000–6. doi:10.1021/bi00833a033. PMID 5785220.
• Malhotra OP, Philip G (1966). "Specificity of goat intestinal esterase". Biochem. Z. 346: 386–402.
• Mentlein R, Schumann M, Heymann E (1984). "Comparative chemical and immunological characterization of five lipolytic enzymes (carboxylesterases) from rat liver microsomes". Arch. Biochem. Biophys. 234 (2): 612–21. doi:10.1016/0003-9861(84)90311-4. PMID 6208846.
• Runnegar MT, Scott K, Webb EC, Zerner B (1969). "Carboxylesterases (EC 3.1.1). Purification and titration of ox liver carboxylesterase". Biochemistry. 8 (5): 2013–8. doi:10.1021/bi00833a035. PMID 5785222.

• Biology

• EC 3.1.1