title: Characterization of SpnQ from the spinosyn biosynthetic pathway of Saccharopolyspora spinosa: mechanistic and evolutionary implications for C-3 deoxygenation in deoxysugar biosynthesis.
abstract: The C-3 deoxygenation step in the biosynthesis of d-forosamine (4-N,N-dimethylamino-2,3,4,6-tetradeoxy-d-threo-hexopyranose), a constituent of spinosyn produced by Saccharopolyspora spinosa, was investigated. The spnQ gene, proposed to encode a TDP-4-keto-2,6-dideoxy-d-glucose 3-dehydratase was cloned and overexpressed in E. coli. Characterization of the purified enzyme established that it is a PMP and iron-sulfur containing enzyme which catalyzes the C-3 deoxygenation in a reductase-dependent manner similar to that of the previously well characterized hexose 3-dehydrase E1 from Yersinia pseudotuberculosis. However, unlike E1, which has evolved to work with a specific reductase partner present in its gene cluster, SpnQ lacks a specific reductase, and works efficiently with general cellular reductases ferredoxin/ferredoxin reductase or flavodoxin/flavodoxin reductase. SpnQ also catalyzes C-4 transamination in the absence of an electron transfer intermediary and in the presence of PLP and l-glutamate. Under the same conditions, both E1 and the related hexose 3-dehydrase, ColD, catalyze C-3 deoxygenation. Thus, SpnQ possesses important features which distinguish it from other well studied homologues, suggesting unique evolutionary pathways for each of the three hexose 3-dehydrases studied thus far.
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Hong
authors.forename: Zongbao
authors.initials: Z
authors.lastname: Zhao
authors.forename: Hung-wen
authors.initials: HW
authors.lastname: Liu
mesh_terms: D002244:Carbon / Q000737:chemistry*; D003837:Deoxy Sugars / Q000096:biosynthesis* / Q000737:chemistry; D018942:Macrolides / Q000737:chemistry / Q000378:metabolism*; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D016930:Saccharopolyspora / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003837:Deoxy Sugars; D018942:Macrolides; D002244:Carbon; D010100:Oxygen