title: Generation of new epothilones by genetic engineering of a polyketide synthase in Myxococcus xanthus.
abstract: Epothilones, potent cytotoxic agents and potential anticancer drugs, are complex polyketides produced by a modular polyketide synthase (PKS). The epothilone PKS genes were introduced and expressed in Myxococcus xanthus and engineered to generate novel unnatural natural products which can be used as new scaffolds for chemical modification. Inactivation of the KR domain in module 6 of the epo PKS resulted in accumulation of 9-oxoepothilone D and its isomer 8-epi-9-oxoepothilone D as the major products. Modification of the KR domain in module 4 resulted in the production of the expected compound 12,13-dihydro-13-oxoepothilone C in trace amounts, and the unexpected compound 11,12-dehydro-12,13-dihydro-13-oxoepothilone D as the major product. The other expected compound, 12,13-dihydro-13-oxoepothilone D, was not detected. The unexpected 13-oxo derivative produced indicates that the ER domain of module 5 has substrate-specificity requirements and suggests a second enzymatic role for the domain.
authors.affiliation: Kosan Biosciences, Inc., 3832 Bay Center Place, Hayward, CA 94545, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Tang
authors.forename: Loleta
authors.initials: L
authors.lastname: Chung
authors.forename: John R
authors.initials: JR
authors.lastname: Carney
authors.forename: Courtney M
authors.initials: CM
authors.lastname: Starks
authors.forename: Peter
authors.initials: P
authors.lastname: Licari
authors.forename: Leonard
authors.initials: L
authors.lastname: Katz
mesh_terms: D019943:Amino Acid Substitution; D000903:Antibiotics, Antineoplastic / Q000096:biosynthesis / Q000737:chemistry; D001483:Base Sequence; D020134:Catalytic Domain / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D034261:Epothilones / Q000096:biosynthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D016254:Mutagenesis, Insertional; D016941:Myxococcus xanthus / Q000201:enzymology* / Q000235:genetics*; D048630:Polyketide Synthases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015202:Protein Engineering; D017434:Protein Structure, Tertiary; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000903:Antibiotics, Antineoplastic; D004269:DNA, Bacterial; D034261:Epothilones; D048630:Polyketide Synthases