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A reverse-phase high-performance liquid chromatography assay for dihydroxy-acid dehydratase.
1Dalton Research Center, Columbia, Missouri.
Analytical Biochemistry
|August 1, 1987
Summary
A new sensitive method quantifies dihydroxy-acid dehydratase activity by measuring alpha-keto acids. This enzyme is crucial for valine and isoleucine biosynthesis, with detection limits as low as 50 pmol.
Area of Science:
- Biochemistry
- Enzymology
- Metabolic pathways
Background:
- Dihydroxy-acid dehydratase is a key enzyme in the biosynthesis of branched-chain amino acids.
- Accurate measurement of its activity is essential for understanding metabolic regulation.
Purpose of the Study:
- To develop and validate a sensitive method for assaying dihydroxy-acid dehydratase activity.
- To quantify enzyme activity in cell-free extracts of Escherichia coli.
Main Methods:
- Enzyme activity assay involving derivatization of alpha-keto acid products with 2,4-dinitrophenylhydrazine.
- Separation and quantification using reverse-phase high-performance liquid chromatography (RP-HPLC) on a C-18 column.
Main Results:
- The method demonstrated high sensitivity, detecting as little as 50 pmol of alpha-ketoisovaleric acid.
- Specific activity of dihydroxy-acid dehydratase in E. coli extracts was measured at 8 mumol/hr/mg protein.
Conclusions:
- The described RP-HPLC method provides a sensitive and reliable means to assay dihydroxy-acid dehydratase activity.
- This technique facilitates further research into amino acid biosynthesis and enzyme kinetics.