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Microsomal flavonoid 3'-monooxygenase from maize seedlings.
1United States Department of Agriculture, Agricultural Research Service, University of Missouri, Columbia, Missouri 65211.
Plant Physiology
|February 1, 1986
Summary
Researchers identified a flavonoid 3'-monooxygenase enzyme in maize, revealing a new step in flavonoid biosynthesis. This cytochrome P-450 enzyme is crucial for understanding plant compound development.
Area of Science:
- Plant Biochemistry
- Molecular Biology
- Maize Genetics
Background:
- Flavonoids are vital plant compounds with diverse roles.
- Previous research focused on the genetics of flavonoid biosynthesis in maize (Zea mays L.).
- The biochemical pathways, particularly hydroxylation steps, remained incompletely understood.
Purpose of the Study:
- To identify and characterize the enzyme responsible for 3'-hydroxylation in maize flavonoid biosynthesis.
- To elucidate the biochemical properties and potential classification of this novel enzyme.
Main Methods:
- Microsomal enzyme preparation from maize seedlings via buffer extraction and ultracentrifugation.
- Enzyme activity assays under varying pH, temperature, and substrate conditions.
- Carbon monoxide inhibition studies and spectrophotometric analysis to identify enzyme type.
- Cytochrome P-450 concentration determination.
Main Results:
- A flavonoid 3'-hydroxylase enzyme was successfully isolated and characterized.
- Enzyme activity was dependent on O(2) and NADPH, optimal at pH 8.5 and 30°C.
- Carbon monoxide inhibition studies and spectral data strongly indicated a cytochrome P-450 monooxygenase.
- Kaempferol, naringenin, and apigenin were identified as substrates.
Conclusions:
- The identification of flavonoid 3'-monooxygenase adds a key enzymatic step to the known maize flavonoid biosynthetic pathway.
- The enzyme is a cytochrome P-450 monooxygenase, providing crucial biochemical insight.
- This discovery bridges genetic and biochemical understanding of flavonoid synthesis in maize.