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Plant-type phytoene desaturase: Functional evaluation of structural implications
Julian Koschmieder1, Mirjam Fehling-Kaschek2, Patrick Schaub1
1University of Freiburg, Faculty of Biology, Freiburg, Germany.
Plos One
|November 28, 2017
Summary
Phytoene desaturase (PDS) enzyme structure reveals substrate channeling in its homotetrameric assembly. Mutagenesis studies suggest a "flavin only" mechanism for herbicide resistance in carotenoid biosynthesis.
Area of Science:
- Biochemistry
- Plant Science
- Enzymology
Background:
- Phytoene desaturase (PDS) is crucial for carotenoid biosynthesis in plants.
- PDS inhibitors, like norflurazon, function as bleaching herbicides.
- The crystal structure of Oryza sativa PDS complexed with norflurazon provides new insights.
Purpose of the Study:
- To investigate the functional implications of the PDS-norflurazon crystal structure.
- To explore substrate channeling and kinetic mechanisms of PDS.
- To assess the potential for engineering herbicide resistance in PDS.
Main Methods:
- Dynamic mathematical modeling of reaction time courses.
- Kinetic investigations and enzyme kinetics.
- Site-directed mutagenesis of conserved residues.
Main Results:
- Evidence supports homotetrameric assembly and substrate channeling of phytofluene.
- PDS follows an ordered ping-pong bi-bi kinetic mechanism.
- Mutagenesis confirms a "flavin only" desaturation mechanism and potential for herbicide resistance engineering.
Conclusions:
- The homotetrameric structure facilitates substrate channeling at membrane surfaces.
- Understanding PDS kinetics and active site is key for herbicide development.
- Targeted mutagenesis can confer herbicide resistance but may impact enzyme activity.
