Abstract text: Polygalacturonases (PGs) are key cell wall–remodelling enzymes that catalyse pectin depolymerization, shaping plant’s primary cell wall architecture. The in vivo regulation of plant PGs remains poorly understood. Here, we identified a novel redox-based mechanism controlling the activity of Arabidopsis thaliana ADPG2. Structural analysis revealed a high number of cysteine residues forming disulfide bridges, particularly in the loops surrounding the active site. We propose that these structural elements act as redox-sensitive switches. We showed that chemical reduction decreases enzymatic activity in vitro, consistent with molecular dynamics (MD) simulations showing changes in loop dynamics between reduced and oxidized states. Site-directed mutagenesis of loop cysteines strongly impaired enzyme activity and processivity without altering global protein structure, demonstrating their regulatory role. We further identified Arabidopsis GILT1 (gamma-inducible thiol reductase 1) as a candidate oxidoreductase mediating this regulation. Microscale thermophoresis confirmed nanomolar binding affinities between ADPG2 and GILT1, supporting a direct interaction while redox proteomic showed reduction of loop cysteines. This mechanism introduces a redox-based layer of PG regulation at the cell wall, providing new insights into the dynamic control of pectin degradation during plant development.