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The biochemical basis for stereochemical control in polyketide biosynthesis
Chiara R Valenzano1, Rachel J Lawson, Alice Y Chen
1Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108, USA.
Polyketide synthases control stereochemistry via ketoreductase domains. Methyl group epimerization occurs after chain elongation, catalyzed by the ketoreductase domain itself.
Area of Science:
- Biochemistry
- Molecular Biology
- Organic Chemistry
Background:
- Complex polyketides feature numerous methyl- and hydroxyl-bearing stereogenic centers.
- Understanding the biochemical control of polyketide stereochemistry is crucial.
Purpose of the Study:
- Investigate the biochemical basis for polyketide stereochemistry control.
- Determine the timing and mechanism of epimerization at methyl-bearing centers.
Main Methods:
- Utilized reconstituted components from modular polyketide synthases.
- Performed a series of incubations to analyze product formation and stereochemistry.
Main Results:
- Product stereochemistry directly correlated with ketoreductase domain intrinsic stereospecificity.
- Methyl group epimerization occurs after ketosynthase-catalyzed chain elongation.
- Epimerization is likely catalyzed by the ketoreductase domain, with minor rate differences observed.
Conclusions:
- Ketoreductase domains are key determinants of polyketide stereochemistry.
- Epimerization at methyl-bearing centers is a post-elongation process.
- The ketoreductase domain itself catalyzes the epimerization reaction.
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