10.1021/ja0649670.s001 Lin Hong Lin Hong Zongbao Zhao Zongbao Zhao Hung-wen Liu Hung-wen Liu Characterization of SpnQ from the Spinosyn Biosynthetic Pathway of <i>Saccharopolyspora spinosa</i>:  Mechanistic and Evolutionary Implications for C-3 Deoxygenation in Deoxysugar Biosynthesis American Chemical Society 2006 reductase partner Yersinia pseudotuberculosis enzyme Evolutionary Implications Characterization Spinosyn Biosynthetic Pathway catalyze SpnQ Saccharopolyspora spinosa PMP TDP spnQ gene electron transfer intermediary PLP dehydrase hexose gene cluster deoxygenation E 1 2006-11-08 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Characterization_of_SpnQ_from_the_Spinosyn_Biosynthetic_Pathway_of_i_Saccharopolyspora_spinosa_i_Mechanistic_and_Evolutionary_Implications_for_C_3_Deoxygenation_in_Deoxysugar_Biosynthesis/3049330 The C-3 deoxygenation step in the biosynthesis of d-forosamine (4-<i>N</i>,<i>N</i>-dimethylamino-2,3,4,6-tetradeoxy-d-<i>threo</i>-hexopyranose), a constituent of spinosyn produced by <i>Saccharopolyspora spinosa</i>, was investigated. The <i>spnQ</i> gene, proposed to encode a TDP-4-keto-2,6-dideoxy-d-glucose 3-dehydratase was cloned and overexpressed in <i>E. coli</i>. 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 E<sub>1</sub> from <i>Yersinia pseudotuberculosis</i>. However, unlike E<sub>1</sub>, 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 E<sub>1</sub> 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.