| Accepted Name |
|---|
| 3-carboxymethyl-3-hydroxy-acyl-[ACP] synthase
|
| Alternative Name(s) |
|---|
| 3-carboxymethyl-3-hydroxy-acyl-[acyl-carrier protein] synthase |
| Reaction catalysed |
|---|
| a 3-oxoacyl-[ACP] + acetyl-[ACP] + H2O = a 3-carboxymethyl-3-hydroxy-acyl-[ACP] + holo-[ACP] + H(+) |
| Comment(s) |
|---|
- This family of enzymes participates in a process that introduces a
methyl branch into nascent polyketide products.
- The process begins with EC 4.1.1.124 which converts the common
extender unit malonyl-[ACP] to acetyl-[ACP]. The enzyme is a mutated
form of a ketosynthase enzyme, in which a Cys residue in the active
site is modified to a Ser residue, leaving the decarboxylase function
intact, but nulifying the ability of the enzyme to form a carbon-
carbon bond.
- Next, EC 2.3.3.22 utilizes the acetyl group to introduce the branch
at the beta position of 3-oxoacyl intermediates attached to a
polyketide synthase, forming a 3-hydroxy-3-carboxymethyl
intermediate.
- This is followed by dehydration catalyzed by EC 4.2.1.181 (often
referred to as an ECH1 domain), leaving a 3-carboxymethyl group and
forming a double bond between the alpha and beta carbons.
- The process concludes with decarboxylation catalyzed by EC 4.1.1.125
(often referred to as an ECH2 domain), leaving a methyl branch at the
beta carbon.
- The enzymes are usually encoded by a cluster of genes referred to as
an "HMGS cassette", based on the similarity of the key enzyme to
EC 2.3.3.10, hydroxymethylglutaryl-CoA synthase.
- While the enzyme is similar to EC 2.3.3.10, it is specific for an
[acyl-carrier protein] (ACP)-bound donor and does not interact with a
CoA substrate as donor.
|
| Cross-references |
|---|
| BRENDA | 2.3.3.22 |
| EC2PDB | 2.3.3.22 |
| ExplorEnz | 2.3.3.22 |
| KEGG Ligand Database for Enzyme Nomenclature | 2.3.3.22 |
| IUBMB Enzyme Nomenclature | 2.3.3.22 |
| MEDLINE | Find literature relating to 2.3.3.22 |
| MetaCyc | 2.3.3.22 |
| Rhea expert-curated reactions | 2.3.3.22 |
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ENZYME /
UniProtKB/Swiss-Prot entries corresponding to 2.3.3.-
All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 2.3.-.-
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