Metal-Dependent 2-Keto-3,6-dideoxy-6-sulfo-gluconate (KDSG) Aldolase: Decoding the Key C─C Bond Cleaving Step in Bacterial Sulfoglycolysis

Abstract

Sulfoquinovose (SQ) is a major biogenic sulfonated sugar whose degradation fuels microbial sulfur and carbon cycling. In the sulfoglycolytic Entner–Doudoroff (sulfo-ED) pathway, 2-keto-3,6-dideoxy-6-sulfogluconate (KDSG) is cleaved by KDSG aldolase to yield pyruvate and sulfolactaldehyde, yet the structure and mechanism of this enzyme have remained unclear. We report the biochemical and structural characterization of a metal-dependent KDSG aldolase from Pseudomonas putida using chemo-enzymatically synthesized KDSG. The enzyme forms a homohexamer, with a (β/α)8 TIM-barrel monomer assembling as a ‘dimer-of-trimers’. The enzyme exhibits optimal activity in the presence of Co2+ or Mn2+, consiste..