title: Sequential action of two flavoenzymes, PgaE and PgaM, in angucycline biosynthesis: chemoenzymatic synthesis of gaudimycin C.
abstract: Tailoring steps in aromatic polyketide antibiotic biosynthesis are an important source of structural diversity and, consequently, an intriguing focal point for enzymological studies. PgaE and PgaM from Streptomyces sp. PGA64 are representatives of flavoenzymes catalyzing early post-PKS reactions in angucycline biosynthesis. This in vitro study illustrates that the chemoenzymatic conversion of UWM6 into the metabolite, gaudimycin C, requires multiple closely coupled reactions to prevent intermediate degradation. The NMR structure of gaudimycin C confirms that the reaction cascade involves C12- and C12b-hydroxylation, C2,3-dehydration, and stereospecific ketoreduction at C6. Enzymatic 18O incorporation studies verify that the oxygens at C12 and C12b derive from O2 and H2O, respectively. The results indicate that PgaM deviates mechanistically from flavoprotein monooxygenases, and suggest an alternative catalytic mechanism involving a quinone methide intermediate.
authors.affiliation: Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland.
authors.forename: Pauli
authors.initials: P
authors.lastname: Kallio
authors.forename: Zhanliang
authors.initials: Z
authors.lastname: Liu
authors.forename: Pekka
authors.initials: P
authors.lastname: Mäntsälä
authors.forename: Jarmo
authors.initials: J
authors.lastname: Niemi
authors.forename: Mikko
authors.initials: M
authors.lastname: Metsä-Ketelä
mesh_terms: D018943:Anthracyclines / Q000378:metabolism*; D000880:Anthraquinones / Q000737:chemistry / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D005420:Flavoproteins / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology*; D014867:Water / Q000378:metabolism
chemical_list: D018943:Anthracyclines; D000880:Anthraquinones; D000900:Anti-Bacterial Agents; D005420:Flavoproteins; C528940:gaudimycin C; D014867:Water; D006899:Mixed Function Oxygenases; D010100:Oxygen