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Gene Review

C4H  -  trans-cinnamate 4-monooxygenase

Arabidopsis thaliana

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Disease relevance of ATC4H


High impact information on ATC4H

  • The increase in sinapate ester accumulation in the mutant is associated with an enhanced expression of the gene encoding cinnamate 4-hydroxylase, which appears to be the principal target of AtMYB4 and an effective rate limiting step in the synthesis of sinapate ester sunscreens [3].
  • In contrast, it shares much less homology with cinnamate-4-hydroxylase, a P450 that catalyzes the hydroxylation of cinnamic acid three steps earlier in the general phenylpropanoid pathway [4].
  • Biochemical characterization of the Arabidopsis ATR1/CYP73A5 and ATR2-1/CYP73A5 systems demonstrates that the two distantly related Arabidopsis reductases similarly support the first oxidative step of the phenylpropanoid general pathway [5].
  • Of the three enzymes originally proposed to hydroxylate the 4-, 3-, and 5-positions of the aromatic ring, cinnamate 4-hydroxylase (C4H), which converts trans-cinnamic acid to p-coumaric acid, is the best characterized and is also the archetypal plant P450 monooxygenase [6].
  • In transgenic Arabidopsis, the promoters of CYP98A3 and C4H showed wound inducibility and a comparable developmental regulation throughout the life cycle, except in seeds, where the CYP98A3 promoter construct was inactive while remaining active in silique walls [6].

Biological context of ATC4H

  • The entire C4H coding sequence plus 2.9 kb of its promoter were isolated on a 5.4-kb HindIII fragment of this cosmid [7].
  • A C4H promoter region of 907 bp contained all of the three cis-acting elements (boxes P, A, and L) conserved among the PAL and 4CL genes so far reported as controlling expression [1].
  • To study the expression of this gene in Arabidopsis thaliana, a C4H cDNA clone from the Arabidopsis expressed sequence tag database was identified and used to isolate its corresponding genomic clone [7].
  • The deduced amino acid sequence is 84.7% identical to that of mung bean C4H and therefore was designated CYP73A5 [1].
  • A full-length cDNA encoding C4H was isolated from a hybrid poplar (Populus trichocarpa x P. deltoides) young leaf cDNA library [8].

Anatomical context of ATC4H

  • Cinnamic acid 4-hydroxylase (C4H), a member of the cytochrome P450 monooxygenase superfamily, plays a central role in phenylpropanoid metabolism and lignin biosynthesis and possibly anchors a phenylpropanoid enzyme complex to the endoplasmic reticulum (ER) [8].
  • Heterologous expression of CYP73A5, an Arabidopsis cytochrome P450 monooxygenase, in baculovirus-infected insect cells yields correctly configured P450 detectable by reduced CO spectral analysis in microsomes and cell lysates [9].

Associations of ATC4H with chemical compounds

  • Immunoblot analysis showed that C4H was present in the microsomal fraction and microsomal preparations from strains expressing both enzymes efficiently converted cinnamic acid to p-coumaric acid with high specific activities [8].
  • Yields of thioglycolic acid and Klason lignin in C4H-F5H lines were lower than in the wild-type, suggesting that F5H over-expression leads to a reduced deposition or an altered extractability of lignin in the transgenic plants [10].
  • Besides its PAL activity, the recombinant PAL enzyme showed tyrosine ammonia lyase activity, which enabled the biosynthesis of naringenin without introducing cinnamate 4-hydroxylase (C4H) [11].
  • For development of high-throughput P450 substrate profiling procedures, membrane proteins derived from cells overexpressing CYP73A5 and/or NADPH P450 reductase were incorporated into soluble His(6)-tagged nanoscale lipid bilayers (Nanodiscs) using a simple self-assembly process [9].
  • CYP73A5 protein co-assembled with P450 reductase into Nanodiscs hydroxylates t-cinnamic acid using reduced pyridine nucleotide as an electron source [9].

Other interactions of ATC4H

  • C4H (CYP73A5) expression was apparently coordinated in Arabidopsis with both PAL1 and 4CL in response to light and wounding [1].
  • On the other hand, the C4H expression patterns exhibited no significant coordination with those of PAL2 and PAL3 [1].
  • Although the light induction of CHS followed a time course similar to that observed with C4H, no induction of CHS was detected upon wounding [1].

Analytical, diagnostic and therapeutic context of ATC4H


  1. Isolation of a cDNA and a genomic clone encoding cinnamate 4-hydroxylase from Arabidopsis and its expression manner in planta. Mizutani, M., Ohta, D., Sato, R. Plant Physiol. (1997) [Pubmed]
  2. Exploring recombinant flavonoid biosynthesis in metabolically engineered Escherichia coli. Watts, K.T., Lee, P.C., Schmidt-Dannert, C. Chembiochem (2004) [Pubmed]
  3. Transcriptional repression by AtMYB4 controls production of UV-protecting sunscreens in Arabidopsis. Jin, H., Cominelli, E., Bailey, P., Parr, A., Mehrtens, F., Jones, J., Tonelli, C., Weisshaar, B., Martin, C. EMBO J. (2000) [Pubmed]
  4. Ferulate-5-hydroxylase from Arabidopsis thaliana defines a new family of cytochrome P450-dependent monooxygenases. Meyer, K., Cusumano, J.C., Somerville, C., Chapple, C.C. Proc. Natl. Acad. Sci. U.S.A. (1996) [Pubmed]
  5. Cloning, yeast expression, and characterization of the coupling of two distantly related Arabidopsis thaliana NADPH-cytochrome P450 reductases with P450 CYP73A5. Urban, P., Mignotte, C., Kazmaier, M., Delorme, F., Pompon, D. J. Biol. Chem. (1997) [Pubmed]
  6. Arabidopsis CYP98A3 mediating aromatic 3-hydroxylation. Developmental regulation of the gene, and expression in yeast. Nair, R.B., Xia, Q., Kartha, C.J., Kurylo, E., Hirji, R.N., Datla, R., Selvaraj, G. Plant Physiol. (2002) [Pubmed]
  7. Cinnamate-4-hydroxylase expression in Arabidopsis. Regulation in response to development and the environment. Bell-Lelong, D.A., Cusumano, J.C., Meyer, K., Chapple, C. Plant Physiol. (1997) [Pubmed]
  8. Functional characterization and subcellular localization of poplar (Populus trichocarpa x Populus deltoides) cinnamate 4-hydroxylase. Ro, D.K., Mah, N., Ellis, B.E., Douglas, C.J. Plant Physiol. (2001) [Pubmed]
  9. Co-incorporation of heterologously expressed Arabidopsis cytochrome P450 and P450 reductase into soluble nanoscale lipid bilayers. Duan, H., Civjan, N.R., Sligar, S.G., Schuler, M.A. Arch. Biochem. Biophys. (2004) [Pubmed]
  10. Modified lignin in tobacco and poplar plants over-expressing the Arabidopsis gene encoding ferulate 5-hydroxylase. Franke, R., McMichael, C.M., Meyer, K., Shirley, A.M., Cusumano, J.C., Chapple, C. Plant J. (2000) [Pubmed]
  11. Metabolic engineering of the phenylpropanoid pathway in Saccharomyces cerevisiae. Jiang, H., Wood, K.V., Morgan, J.A. Appl. Environ. Microbiol. (2005) [Pubmed]
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