title: Recent advances in combinatorial biosynthesis for drug discovery.
abstract: Because of extraordinary structural diversity and broad biological activities, natural products have played a significant role in drug discovery. These therapeutically important secondary metabolites are assembled and modified by dedicated biosynthetic pathways in their host living organisms. Traditionally, chemists have attempted to synthesize natural product analogs that are important sources of new drugs. However, the extraordinary structural complexity of natural products sometimes makes it challenging for traditional chemical synthesis, which usually involves multiple steps, harsh conditions, toxic organic solvents, and byproduct wastes. In contrast, combinatorial biosynthesis exploits substrate promiscuity and employs engineered enzymes and pathways to produce novel "unnatural" natural products, substantially expanding the structural diversity of natural products with potential pharmaceutical value. Thus, combinatorial biosynthesis provides an environmentally friendly way to produce natural product analogs. Efficient expression of the combinatorial biosynthetic pathway in genetically tractable heterologous hosts can increase the titer of the compound, eventually resulting in less expensive drugs. In this review, we will discuss three major strategies for combinatorial biosynthesis: 1) precursor-directed biosynthesis; 2) enzyme-level modification, which includes swapping of the entire domains, modules and subunits, site-specific mutagenesis, and directed evolution; 3) pathway-level recombination. Recent examples of combinatorial biosynthesis employing these strategies will also be highlighted in this review.
authors.affiliation: Metabolic Engineering Research Laboratory, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research, Singapore.
authors.forename: Huihua
authors.initials: H
authors.lastname: Sun
authors.affiliation: Metabolic Engineering Research Laboratory, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research, Singapore.
authors.forename: Zihe
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Metabolic Engineering Research Laboratory, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research, Singapore ; Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Metabolic Engineering Research Laboratory, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research, Singapore.
authors.forename: Ee Lui
authors.initials: EL
authors.lastname: Ang
mesh_terms: D001688:Biological Products / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D055808:Drug Discovery; D004798:Enzymes / Q000378:metabolism; D006801:Humans
chemical_list: D001688:Biological Products; D004798:Enzymes
keywords: biosynthetic pathways; combinatorial biosynthesis; drug discovery; natural products; nonribosomal peptide synthetases; polyketide synthases