biostudies-literatureNivina AFondation pour la Recherche MedicaleNational Institute of General Medical SciencesNIGMS NIH HHSNational Science FoundationDivision of Graduate Education12524-12547https://www.ebi.ac.uk/biostudies/studies/S-EPMC6935866biostudies-literatureUnknown119(24)Assembly-line polyketide synthases (PKSs) are among the most complex protein machineries known in nature, responsible for the biosynthesis of numerous compounds used in the clinic. Their present-day diversity is the result of an evolutionary path that has involved the emergence of a multimodular architecture and further diversification of assembly-line PKSs. In this review, we provide an overview of previous studies that investigated PKS evolution and propose a model that challenges the currently prevailing view that gene duplication has played a major role in the emergence of multimodularity. We also analyze the ensemble of orphan PKS clusters sequenced so far to evaluate how large the entire diversity of assembly-line PKS clusters and their chemical products could be. Finally, we examine the existing techniques to access the natural PKS diversity in natural and heterologous hosts and describe approaches to further expand this diversity through engineering.Chemical reviewsEvolution and Diversity of Assembly-Line Polyketide Synthases.PMC6935866DGE -1656518R01 GM087934SPE20170336834DGE 1656518F32 GM123637Nivina AHsu JKhosla CYuet KPfalseEvolution and Diversity of Assembly-Line Polyketide Synthases.Assembly-line polyketide synthases (PKSs) are among the most complex protein machineries known in nature, responsible for the biosynthesis of numerous compounds used in the clinic. Their present-day diversity is the result of an evolutionary path that has involved the emergence of a multimodular architecture and further diversification of assembly-line PKSs. In this review, we provide an overview of previous studies that investigated PKS evolution and propose a model that challenges the currently prevailing view that gene duplication has played a major role in the emergence of multimodularity. We also analyze the ensemble of orphan PKS clusters sequenced so far to evaluate how large the entire diversity of assembly-line PKS clusters and their chemical products could be. Finally, we examine the existing techniques to access the natural PKS diversity in natural and heterologous hosts and describe approaches to further expand this diversity through engineering.2019-01-01T00:00:00Z2019 Dec2025-06-01T03:25:36.585Z2025-04-05T16:20:57.905ZS-EPMC69358663183884210.1021/acs.chemrev.9b00525