Polyketide synthase
Polyketide synthases (PKSs) are a family of multi-domain enzymes or enzyme complexes that produce polyketides, a large class of secondary metabolites, in bacteria, fungi, plants, and a few animal lineages. The biosyntheses of polyketides share striking similarities with fatty acid biosynthesis.
The PKS genes for a certain polyketide are usually organized in one operon in bacteria and in gene clusters in eukaryotes.
PKSs can be classified into three groups:
Type I PKSs are further subdivided:
Iterative PKSs (IPKSs) can be still further subdivided:
Each type I polyketide-synthase module consists of several domains with defined functions, separated by short spacer regions. The order of modules and domains of a complete polyketide-synthase is as follows (in the order N-terminus to C-terminus):
Domains:
The polyketide chain and the starter groups are bound with their carboxy functional group to the SH groups of the ACP and the KS domain through a thioester linkage: R-C(=O)OH + HS-protein <=> R-C(=O)S-protein + H2O.
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