Display options
Share it on

Plant Physiol. 1994 Oct;106(2):633-642. doi: 10.1104/pp.106.2.633.

Characterization of Flavonoid 3[prime],5[prime]-Hydroxylase in Microsomal Membrane Fraction of Petunia hybrida Flowers.

Plant physiology

JGT. Menting, R. K. Scopes, T. W. Stevenson

Affiliations

  1. Centre for Protein and Enzyme Technology, Department of Biochemistry, La Trobe University, Bundoora, Victoria, Australia, 3083 (J.G.T.M., R.K.S.).

PMID: 12232356 PMCID: PMC159570 DOI: 10.1104/pp.106.2.633

Abstract

We have detected a flavonoid 3[prime],5[prime]-hydroxylase (F3[prime],5[prime]H) in the microsomal fraction of Petunia hybrida flowers. Activity varied with the development of flowers, peaking immediately prior to and during anthesis, but was absent in mature flowers. F3[prime],5[prime]H activity in flower extracts from genetically defined floral color mutants correlated strictly with the genotypes Hf1 and Hf2. No activity was detected in flowers from mutants homozygous recessive for both alleles. F3[prime],5[prime]H activity was dependent on NADPH and molecular oxygen; there was only slight activity with NADH. The enzyme catalyzes the hydroxylation of 5,7,4[prime]-trihydroxyflavonone at the 3[prime] and 5[prime] positions, and of 5,7,3[prime],4[prime]-tetrahydroxyflavonone and dihydroquercetin at the 5[prime] position. Hydroxylase activity was inhibited by plant growth regulators (1-aminobenzotriazole and tetcyclacis) and by CO, N-ethylmaleimide, diethyldithiocarbamate, and cytochrome (Cyt) c. Activity was not affected by diethylpyrocarbonate or phenylmethylsulfonyl fluoride, but was enhanced by 2-mercaptoethanol. A polyclonal antibody that inhibits higher plant NADPH-Cyt P450 reductase inhibited the F3[prime],5[prime]H. The data are consistent with the suggestion that the P. hybrida F3[prime],5[prime]H is a monooxygenase consisting of a Cyt P450 and a NADPH-Cyt P-450 reductase. Cyts P450 were detected in microsomal membranes and in solubilized detergent extracts of these membranes. F3[prime],5[prime]H activity was sensitive to low concentrations of all detergents tested, and therefore solubilization of the active enzyme was not achieved. Reaction products other than flavanones were observed in F3[prime],5[prime]H assays and these may be formed by enzymic oxidation of flavanones. The possibility of a microsomal flavone synthase of a type that has not been described in P. hybrida is discussed.

References

  1. Biochimie. 1987 Jun-Jul;69(6-7):743-52 - PubMed
  2. J Biol Chem. 1993 Jan 15;268(2):823-31 - PubMed
  3. Plant Physiol. 1994 Oct;106(2):643-50 - PubMed
  4. Biochemistry. 1976 Mar 9;15(5):1097-102 - PubMed
  5. J Biol Chem. 1964 Jul;239:2370-8 - PubMed
  6. Arch Biochem Biophys. 1982 Jul;216(2):522-9 - PubMed
  7. Anal Biochem. 1985 Oct;150(1):76-85 - PubMed
  8. Arch Biochem Biophys. 1989 Sep;273(2):543-53 - PubMed
  9. Plant Physiol. 1989 Apr;89(4):1141-9 - PubMed
  10. Arch Biochem Biophys. 1957 Jun;68(2):501-2 - PubMed
  11. Plant Physiol. 1991 Jul;96(3):669-74 - PubMed
  12. Can J Physiol Pharmacol. 1990 Sep;68(9):1278-85 - PubMed
  13. Biochem J. 1988 Jun 1;252(2):537-43 - PubMed
  14. Plant Physiol. 1986 Feb;80(2):483-6 - PubMed
  15. Anal Biochem. 1977 May 1;79(1-2):544-52 - PubMed
  16. J Biol Chem. 1971 Jun 25;246(12):3870-8 - PubMed
  17. Nature. 1993 Nov 18;366(6452):276-9 - PubMed
  18. Plant Physiol. 1976 Oct;58(4):479-84 - PubMed
  19. Eur J Biochem. 1983 Aug 15;134(3):547-54 - PubMed

Publication Types