title: Biosynthetic characterization and chemoenzymatic assembly of the cryptophycins. Potent anticancer agents from cyanobionts.
abstract: The lichen cyanobacterial symbiont Nostoc sp. ATCC 53789 and its close relative Nostoc sp. GSV 224 are prolific producers of natural products, generating >25 derivatives of the cryptophycin class of secondary metabolites. Cryptophycin 1, the prototypic member of the class, is a potent tubulin-depolymerizing agent, and several semisynthetic derivatives are being developed as anticancer therapeutics. Here we provide a detailed characterization of the cryptophycin metabolic pathway by stable-isotope labeling experiments and through cloning, sequencing, and annotating the cryptophycin biosynthetic gene cluster. A comparative secondary metabolomic analysis based on polyketide (PK)/non-ribosomal peptide gene clusters from the phylogenetically related, non-cryptophycin producing cycad symbiont, Nostoc punctiforme ATCC 29133, was used to identify the cryptophycin biosynthetic genes that encompass approximately 40 kb within the lichen symbiont Nostoc sp. ATCC 53789 genome. The pathway encodes a collinear set of enzymes, including three modular PK synthases, two non-ribosomal peptide synthetase modules, and an integrated adenylation/ketoreductase didomain for elaboration of the leucic acid subunit. In addition, genes encoding key tailoring steps, including a FAD-dependent halogenase and CYP450 epoxidase, were identified. The inherent flexibility of the cryptophycin biosynthetic enzymes was harnessed to generate a suite of new analogues by altering the pool of PK starter units and selected amino acid extender groups. Characterization of the cryptophycin CYP450 enabled development of the first stereospecific synthesis of cryptophycin 2, through a tandem chemoenzymatic synthesis from the natural seco-cryptophycin 4 chain elongation intermediate.
authors.affiliation: Department of Microbiology and BioTechnology Institute, University of Minnesota, Minneapolis-St. Paul, Minnesota 55108, USA.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Magarvey
authors.forename: Zachary Q
authors.initials: ZQ
authors.lastname: Beck
authors.forename: Trimurtulu
authors.initials: T
authors.lastname: Golakoti
authors.forename: Yousong
authors.initials: Y
authors.lastname: Ding
authors.forename: Udo
authors.initials: U
authors.lastname: Huber
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Hemscheidt
authors.forename: Dafna
authors.initials: D
authors.lastname: Abelson
authors.forename: Richard E
authors.initials: RE
authors.lastname: Moore
authors.forename: David H
authors.initials: DH
authors.lastname: Sherman
mesh_terms: D000595:Amino Acid Sequence; D000903:Antibiotics, Antineoplastic / Q000096:biosynthesis / Q000138:chemical synthesis / Q000737:chemistry; D003001:Cloning, Molecular; D047630:Depsipeptides / Q000096:biosynthesis / Q000138:chemical synthesis / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D046937:Nostoc / Q000201:enzymology / Q000378:metabolism*; D010453:Peptide Synthases / Q000235:genetics*; D048630:Polyketide Synthases / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D000903:Antibiotics, Antineoplastic; D047630:Depsipeptides; D048630:Polyketide Synthases; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase