Journal article
The Roles of a Flavone-6-Hydroxylase and 7-O-Demethylation in the Flavone Biosynthetic Network of Sweet Basil
The Journal of biological chemistry, Vol.288(3), pp.1795-1805
01/18/2013
Handle:
https://hdl.handle.net/2376/103434
PMCID: PMC3548489
PMID: 23184958
Abstract
Background:
Late steps of lipophilic flavone biosynthesis in mints are unknown.
Results:
CYP82D monooxygenases catalyze 6-hydroxylation of 7-
O
-methylated precursor, whose 7-methyl group is subsequently removed by demethylation in basil but not in peppermint.
Conclusion:
Flavone biosynthesis in basil involves an unusual loop.
Significance:
Novel mechanisms elucidated in basil suggest a new hypothesis for similar metabolic networks in other plants.
Lipophilic flavonoids found in the Lamiaceae exhibit unusual 6- and 8-hydroxylations whose enzymatic basis is unknown. We show that crude protein extracts from peltate trichomes of sweet basil (
Ocimum basilicum
L.) cultivars readily hydroxylate position 6 of 7-
O
-methylated apigenin but not apigenin itself. The responsible protein was identified as a P450 monooxygenase from the CYP82 family, a family not previously reported to be involved in flavonoid metabolism. This enzyme prefers flavones but also accepts flavanones
in vitro
and requires a 5-hydroxyl in addition to a 7-methoxyl residue on the substrate. A peppermint (
Mentha
×
piperita
L.) homolog displayed identical substrate requirements, suggesting that early 7-
O
-methylation of flavones might be common in the Lamiaceae. This hypothesis is further substantiated by the pioneering discovery of 2-oxoglutarate-dependent flavone demethylase activity in basil, which explains the accumulation of 7-
O
-demethylated flavone nevadensin.
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Details
- Title
- The Roles of a Flavone-6-Hydroxylase and 7-O-Demethylation in the Flavone Biosynthetic Network of Sweet Basil
- Creators
- Anna Berim - From the Institute of Biological Chemistry Washington State University, Pullman, Washington 99164-6340David R Gang - From the Institute of Biological Chemistry Washington State University, Pullman, Washington 99164-6340
- Publication Details
- The Journal of biological chemistry, Vol.288(3), pp.1795-1805
- Academic Unit
- Biological Chemistry, Institute of
- Publisher
- American Society for Biochemistry and Molecular Biology; 9650 Rockville Pike, Bethesda, MD 20814, U.S.A
- Identifiers
- 99900546658801842
- Language
- English
- Resource Type
- Journal article