Poster Presentation Royal Australian Chemical Institute National Congress 2026

Molecular characterization of an Fe(II)/α-ketoglutarate-dependent sulfoquinovose dioxygenase (#417)

Ho Ho 1 , Mihwa Lee 1 , Spencer Williams 1 , Guy Jameson 1 , Megan Maher 1
  1. The University of Melbourne, Melbourne, VICTORIA, Australia

Sulfoquinovose (SQ; 6-deoxy-6-sulfoglucose) is a widespread sulfosugar produced by photosynthetic organisms and assimilated by bacteria. The sulfoquinovose dioxygenase (SqoD) pathway enables complete utilization of the six-carbon skeleton of SQ and involves direct C–S bond cleavage by an Fe(II)/α-ketoglutarate (αKG)–dependent sulfoquinovose dioxygenase. To define the molecular basis of this transformation, we determined crystal structures of SqoD from Marinobacterium aestuarii in multiple coordination states, using Mn2+ as an inactive surrogate for Fe2+. Complementary steady-state and pre-steady-state kinetic analyses revealed key catalytic intermediates, including the Fe(IV)=O species and enzyme-bound α-hydroxysulfonate (6-sulfoglucose) and 6-dehydroglucose. X-ray structures of SqoD in complex with SQ, Mn2+, and αKG reveal a canonical 2-His-1-carboxylate facial triad coordinating the metal center and define how SQ is positioned within the active site for catalysis. Together, these data establish the structural and mechanistic framework for SqoD activity, providing direct molecular insight into SQ C–S bond cleavage and a central step in bacterial sulfosugar catabolism.

Keywords: organosulfur, Fe(II)/α-ketoglutarate-dependent dioxygenase, steady-state and pre-steady-state kinetic analyses, X-ray crystallography, sulfur metabolism

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