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 + H
2O
an alcohol + a carboxylate
Most enzymes from this group are
serine hydrolase Serine hydrolases are one of the largest known enzyme classes comprising approximately ~200 enzymes or 1% of the genes in the human proteome. A defining characteristic of these enzymes is the presence of a particular serine at the active site, which ...
s belonging to the superfamily of proteins with
α/β hydrolase fold. Some exceptions include an esterase with
β-lactamase
Beta-lactamases, (β-lactamases) are enzymes () produced by bacteria that provide multi-resistance to beta-lactam antibiotics such as penicillins, cephalosporins, cephamycins, monobactams and carbapenems ( ertapenem), although carbapenems ...
-like structure ().
Carboxylesterases are widely distributed in nature, and are common in mammalian liver. Many participate in
phase I metabolism of
xenobiotics
A xenobiotic is a chemical substance found within an organism that is not naturally produced or expected to be present within the organism. It can also cover substances that are present in much higher concentrations than are usual. Natural compo ...
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
C20 H32 O2; 20:
4,
n-6), formed by the synthesis from dietary
linoleic acid
Linoleic acid (LA) is an organic compound with the formula COOH(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are ''cis''. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 ''cis''-9,12. A linoleate is a salt or ester of this acid.
...
(LA: C
18H
32O
2 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
Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar ...
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
Further reading
*
*
*
*
*
*
*
*
{{Portal bar, Biology, border=no
EC 3.1.1