Biosynthetic Innovation on A Polyketide Assembly Line: Biochemical Studiesof Curacin A Pathway.

[摘要] The chemical diversity of natural products is fueled by the emergence and ongoingevolution of biosynthetic pathways in secondary metabolism. However, enzyme evolutionin natural product assembly lines, especially the co-evolution of enzymes as functionalassemblies for metabolic diversification, is not well understood, especially at thebiochemical level. The biosynthetic pathway of curacin A, a marine cyanobacterialmetabolite from Lyngbya majuscula possessing anti-mitotic and anti-proliferative activity,provides us intriguing opportunities to reveal the evolutionary events on the polyketidepathway.My Ph.D. research is focused on biochemical studies of the chain initiation,cyclopropane formation and chain termination steps in curacin A pathway. We identifiedand characterized a set of unusual enzymes that catalyze GNAT-like polyketide chaininitiation, polyketide HMG β-branching, chlorination, cyclopropanation, anddecarboxylative polyketide chain termination steps. Heterologous protein expression andenzyme purification, mutagenesis, biochemical assays, mass spectrometry and X-raycrystallography have been employed in our studies. These enzymes with attractivebiochemical features significantly expand the catalytic repertoire of nature productbiosynthesis, as well as provide ideal objects for evolutionary biologists and mechanisticenzymologists.Based on our studies, different types of metabolic evolution are observed, including1) the insertion of gene assemblies by homologous recombination, 2) recruitment of newenzymes to change biochemical schemes and functional group placement, 3)development of new functions from canonical enzyme scaffolds, and 4) diversification ofregiochemical controls for pathway diversification. As such, our biochemical studies cansignificantly advance the knowledge of natural product biosynthesis, enzyme evolutionand mechanistic enzymology.

[发布机构] University of Michigan

[效力级别] GNAT

[关键词] Biosynthesis of Natural Products;GNAT;Cyclopropane;Polyketide Beta-branching;Halogenase;Sulfotransferase;Biological Chemistry;Science;Medicinal Chemistry