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Directed evolution experiments reveal mutations at cycloartenol synthase residue His477 that dramatically alter
Michael J R Segura1, Silvia Lodeiro, Michelle M Meyer
1Department of Chemistry, Rice University, Houston, Texas 77005, USA.
Organic Letters
|December 6, 2002
Summary
Researchers identified specific mutations in cycloartenol synthase, an enzyme involved in sterol biosynthesis. These mutations alter the enzyme's activity, leading to the production of lanosterol and parkeol, key sterol compounds.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Cycloartenol synthase (CAS) catalyzes the cyclization and rearrangement of oxidosqualene to the protosteryl cation.
- This enzyme plays a crucial role in plant sterol biosynthesis, ultimately forming cycloartenol.
- Understanding CAS function is vital for elucidating sterol metabolic pathways.
Purpose of the Study:
- To identify cycloartenol synthase mutants with altered deprotonation specificities.
- To investigate the impact of specific mutations on the production of lanosterol and parkeol.
- To generate novel enzymes with enhanced lanosterol and parkeol synthase activities.
Main Methods:
- Random mutagenesis of cycloartenol synthase was performed.
- Mutant enzymes were selected using a yeast lanosterol synthase mutant.
- Product analysis was conducted to determine the types and ratios of sterols produced.
Main Results:
- A His477Asn mutant was identified, producing 88% lanosterol and 12% parkeol.
- A His477Gln mutant yielded 73% parkeol, 22% lanosterol, and 5% Delta(7)-lanosterol.
- These mutants represent highly efficient lanosterol and parkeol synthases generated through mutagenesis.
Conclusions:
- Specific mutations in cycloartenol synthase can significantly alter its catalytic activity and product specificity.
- The His477Asn and His477Gln mutants demonstrate novel deprotonation pathways, leading to increased lanosterol and parkeol production.
- This study provides valuable tools for investigating sterol biosynthesis and developing enzymes with tailored activities.