Carboxylesterase
Template:Short description Template:Infobox enzyme The enzyme carboxylesterase (or carboxylic-ester hydrolase, EC 3.1.1.1; systematic name carboxylic-ester hydrolase) catalyzes reactions of the following form:[1]
- a carboxylic ester + H2O 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 (Template:PDB).
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.[2]
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:
An approved nomenclature has been established for the five mammalian carboxylesterase gene families.[3]