The roles of a flavone-6-hydroxylase and 7-O-demethylation in the flavone biosynthetic network of sweet basil

J Biol Chem. 2013 Jan 18;288(3):1795-805. doi: 10.1074/jbc.M112.420448. Epub 2012 Nov 26.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Apigenin / metabolism
  • Chromatography, High Pressure Liquid
  • Cytochrome P-450 Enzyme System / chemistry
  • Cytochrome P-450 Enzyme System / classification
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism*
  • Flavanones / metabolism
  • Flavones / metabolism*
  • Mass Spectrometry
  • Mentha piperita / genetics
  • Mentha piperita / metabolism*
  • Molecular Sequence Data
  • Ocimum basilicum / genetics
  • Ocimum basilicum / metabolism*
  • Phylogeny
  • Plant Extracts / chemistry
  • Plant Leaves / chemistry
  • Plant Proteins / chemistry
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Substrate Specificity

Substances

  • Flavanones
  • Flavones
  • Plant Extracts
  • Plant Proteins
  • nevadensin
  • Apigenin
  • Cytochrome P-450 Enzyme System
  • flavonoid 6-hydroxylase

Associated data

  • GENBANK/JX162212
  • GENBANK/JX162213
  • GENBANK/JX162214
  • GENBANK/JX524270