Engineered GH3 enzymes for targeted inactivation of 2,4-D herbicide through amino acid conjugation

Overview

This research program focuses on engineering GH3 acyl acid amido synthetases—enzymes naturally found in plants—to inactivate the broadleaf herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) through amino acid conjugation. The team has demonstrated that the Arabidopsis enzyme AtGH3.15 catalyzes the rapid conjugation of amino acids to the structurally related herbicide 2,4-DB, representing the first known GH3 protein with activity toward a synthetic herbicide. Using structural insights from X-ray crystallography, the project aims to redesign enzyme active sites to shift substrate preference toward 2,4-D, enabling new approaches to herbicide management, crop selectivity, and environmental bioremediation.

Technical specifications

Core technology:

• Structure-guided mutagenesis of GH3 acyl acid amido synthetases
• Two parallel engineering strategies targeting AtGH3.15 (optimized for 2,4-DB) and AtGH3.5 (preference for small aromatic acids related to 2,4-D)
• Mutant library generation guided by X-ray crystal structures of enzyme-herbicide complexes
• Biochemical activity screening across phenoxyalkanoic and phenylalkyl acid substrates

Key findings to date:

• AtGH3.15 displays high catalytic activity with 2,4-DB and broad amino acid substrate range
• Side-chain length of alkanoic and alkyl acids is a critical determinant of substrate preference
• Crystal structure of the AtGH3.15•2,4-DB complex reveals herbicide binding geometry in the active site
• Arabidopsis knockout and overexpression lines show expected hypersensitivity and tolerance phenotypes in root elongation assays with 2,4-DB

Technology readiness level

The program is at an early-to-mid stage of development. Published biochemical and structural characterization of AtGH3.15 has established proof-of-concept for GH3-mediated herbicide conjugation. Current work focuses on active-site mutagenesis to redirect activity toward 2,4-D, followed by mutant library screening and activity validation. Downstream applications in transgenic crop engineering, herbicide selectivity, or bioremediation would require additional development beyond the current enzyme engineering phase.