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PROSITE documentation PDOC00112 [for PROSITE entry PS00122]

Carboxylesterases type-B signatures


Higher eukaryotes have many distinct esterases. Among the different types are those which act on carboxylic esters (EC 3.1.1.-). Carboxyl-esterases have been classified into three categories (A, B and C) on the basis of differential patterns of inhibition by organophosphates. The sequence of a number of type-B carboxylesterases indicates [1,2,3] that the majority are evolutionary related. This family currently consists of the following proteins:

  • Acetylcholinesterase (EC (AChE) from vertebrates and from Drosophila.
  • Mammalian cholinesterase II (butyryl cholinesterase) (EC Acetylcholinesterase and cholinesterase II are closely related enzymes that hydrolyze choline esters [4].
  • Mammalian liver microsomal carboxylesterases (EC
  • Drosophila esterase 6, produced in the anterior ejaculatory duct of the male insect reproductive system where it plays an important role in its reproductive biology.
  • Drosophila esterase P.
  • Culex pipiens (mosquito) esterases B1 and B2.
  • Myzus persicae (peach-potato aphid) esterases E4 and FE4.
  • Mammalian bile-salt-activated lipase (BAL) [5], a multifunctional lipase which catalyzes fat and vitamin absorption. It is activated by bile salts in infant intestine where it helps to digest milk fats.
  • Insect juvenile hormone esterase (JH esterase) (EC
  • Lipases (EC from the fungi Geotrichum candidum and Candida rugosa.
  • Caenorhabditis gut esterase (gene ges-1).
  • Duck acyl-[acyl-carrier protein] hydrolase, medium chain (EC, an enzyme that may be associated with peroxisome proliferation and may play a role in the production of 3-hydroxy fatty acid diester pheromones.
  • Membrane enclosed crystal proteins from slime mold. These proteins are, most probably esterases; the vesicles where they are found have therefore been termed esterosomes.

So far two bacterial proteins have been found to belong to this family:

  • Phenmedipham hydrolase (phenylcarbamate hydrolase), an Arthrobacter oxidans plasmid-encoded enzyme (gene pcd) that degrades the phenylcarbamate herbicides phenmedipham and desmedipham by hydrolyzing their central carbamate linkages.
  • Para-nitrobenzyl esterase from Bacillus subtilis (gene pnbA).

The following proteins, while having lost their catalytic activity, contain a domain evolutionary related to that of carboxylesterases type-B:

  • Thyroglobulin (TG), a glycoprotein specific to the thyroid gland, which is the precursor of the iodinated thyroid hormones thyroxine (T4) and triiodo thyronine (T3).
  • Drosophila protein neurotactin (gene nrt) which may mediate or modulate cell adhesion between embryonic cells during development.
  • Drosophila protein glutactin (gene glt), whose function is not known.

As is the case for lipases and serine proteases, the catalytic apparatus of esterases involves three residues (catalytic triad): a serine, a glutamate or aspartate and a histidine. The sequence around the active site serine is well conserved and can be used as a signature pattern. As a second signature pattern, we selected a conserved region located in the N-terminal section and which contains a cysteine involved in a disulfide bond.


Human esterase-D, also a type-B carboxylesterase, does not seem to be evolutionary related.

Expert(s) to contact by email:

Sussman J.

Last update:

April 2006 / Pattern revised.

Technical section

PROSITE methods (with tools and information) covered by this documentation:

CARBOXYLESTERASE_B_1, PS00122; Carboxylesterases type-B serine active site  (PATTERN)

CARBOXYLESTERASE_B_2, PS00941; Carboxylesterases type-B signature 2  (PATTERN)


1AuthorsMyers M. Richmond R.C. Oakeshott J.G.
TitleOn the origins of esterases.
SourceMol. Biol. Evol. 5:113-119(1988).
PubMed ID3163407

2AuthorsKrejci E. Duval N. Chatonnet A. Vincens P. Massoulie J.
TitleCholinesterase-like domains in enzymes and structural proteins: functional and evolutionary relationships and identification of a catalytically essential aspartic acid.
SourceProc. Natl. Acad. Sci. U.S.A. 88:6647-6651(1991).
PubMed ID1862088

3AuthorsCygler M. Schrag J.D. Sussman J.L. Harel M. Silman I. Gentry M.K. Doctor B.P.
TitleRelationship between sequence conservation and three-dimensional structure in a large family of esterases, lipases, and related proteins.
SourceProtein Sci. 2:366-382(1993).
PubMed ID8453375

4AuthorsLockridge O.
TitleStructure of human serum cholinesterase.
SourceBioEssays 9:125-128(1988).
PubMed ID3067729

5AuthorsWang C.-S. Hartsuck J.A.
TitleBile salt-activated lipase. A multiple function lipolytic enzyme.
SourceBiochim. Biophys. Acta 1166:1-19(1993).
PubMed ID8431483

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