Structural and chemical trapping of flavin-oxide intermediates reveals substrate-directed reaction multiplicity.

ABSTRACT: Though reactive flavin-N5/C4α-oxide intermediates can be spectroscopically profiled for some flavin-assisted enzymatic reactions, their exact chemical configurations are hardly visualized. Structural systems biology and stable isotopic labelling techniques were exploited to correct this stereotypical view. Three transition-like complexes, the α-ketoacid…N5-FMN_ox complex (I), the FMN_ox -N5-aloxyl-C'α^- -C4α⁺ zwitterion (II), and the FMN-N5-ethenol-N5-C4α-epoxide (III), were determined from mandelate oxidase (Hmo) or its mutant Y128F (monooxygenase) crystals soaked with monofluoropyruvate (a product mimic), establishing that N5 of FMN_ox an alternative reaction center can polarize to an ylide-like mesomer in the active site. In contrast, f

SUBMITTER: Lin KH 

PROVIDER: S-EPMC7314388 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature