Table 5.
Diversity of polyketide synthases in microbes
| Microbes | Type of polyketide synthase | Protein structure | Functional characterization | Types of polyketides produced | Domain organization |
|---|---|---|---|---|---|
| Bacteria | Type I (modular) | Single linear protein with multiple modules | Active site used only once | Macrolide polyketides, such as the erythromycin A and rifamycin | e.g. Saccharopolyspora erythrea KS-AT-ACP-KR-TE = KS-AT-ACP-KR-TE = KS-AT-ACP-KR-TE = KS-AT-ACP-KR-TE |
| Bacteria | Type II (Iterative) | Multiple proteins, with a single mono-functional active site | Active sites may be used only once or repeatedly | Aromatic polyketides, such as actinorhodin and tetracenomycin | e.g. Streptomyces coelicolor KS-AT-ACP-KR-DH-ER |
| Bacteria | Type III (Iterative) | One protein with multiple modules | Active sites are reused repeatedly | Dihydroxyphenylalanine melanins | e.g. bacterial PKS Streptomyces grieseus (RppA) KS-AT-ACP-TE |
| Fungi | Type I (iterative) | Single protein with one module | Active sites are reused repeatedly | Lovastatins, Aflatoxins, Melanin | e.g. polyketide synthase (LovF) from A. terreus KS-AT-DH-MT-(ER)-KR -ACP |
| Fungi | Type III | One protein with multiple modules | Active sites are reused repeatedly | 3,5-dihydroxybenzoic acid | e.g. CsyA from A. oryzae KS-AT-ACP-KR-MT-DH-ER |
| Plants | Type III (Iterative) | One protein with multiple modules | Active sites are reused repeatedly | Flavonoids like chalcones and stilbenes | e.g. Chalcone synthase from Medicago sativa |