Phenylpropanoid metabolism

Antioxidant potential of intermediates in phenylpropanoid metabolism in higher FEBS Letters, 368, 188-92. 

Humphreys, J. M. Hemm, M. R. Chappie, C. Ferulate 5-hydroxylase fromArahidopsis is a multifunctional cytochrome P450-dependent monooxygenase catalyzing parallel hydroxylations in phenylpropanoid metabolism. Proc. Natl. Acad Sci. USA 1999, 96, 10045-10050. 

DIXON, R.A., PAIVA, N.L., Stress-induced phenylpropanoid metabolism, Plant Cell, 1995, 7,1085-1097. 

Dixon RA, Achnine L, Kota P, Liu CJ, Reddy MSS, Wang LJ (2002) The phenylpropanoid pathway and plant defence - a genomics perspective. Mol Plant Pathol 3 371-390 Dixon RA, Paiva NL (1995) Stress-induced phenylpropanoid metabolism. Plant Cell 7 1085-1097... 

Ritter H, Schulz GE (2004) Structural basis for the entrance into the phenylpropanoid metabolism catalyzed by phenylalanine ammonia-lyase. Plant Cell 16(12) 3426-3436... 

Sukrasno N, Yeoman MM (1993) Phenylpropanoid metabolism during growth and development of Capsicum frutescens fruits. Phytochemistry 32 839-844... 

Hahlbrock K, Scheel D (1989) Physiology and molecular biology of phenylpropanoid metabolism. Annu Rev Plant Physiol Plant Mol Biol 40 347-369... 

Seshime Y et ai, Genomic evidences for the existence of a phenylpropanoid metabolic pathway m Aspergillus oryzae, Biochem Biophys Res Commun 337 747-751,2005. 

The chemical and physical evidence for the presence of lignin in the material deposited at wound margins is supported by biochemical studies on the enzymes involved in phenylpropanoid metabolism. Thus, the extractable activities of phenylalanine ammonia-lyase, tyrosine ammonia-lyase, cinnamate-4-hydroxylase, caffeic acid O-methyltransferase,... 

Franke, R. et al.. The Arabidopsis REFS gene encodes the 3-hydroxylase of phenylpropanoid metabolism. Plant J., 30, 33, 2002. 

The observations that flavonols are not involved in the fertilization process in certain species, and that this function can be completed using other compounds, suggest that flavonols only affect fertility indirectly. There are various examples of cross-talk between branch pathways of phenylpropanoid metabolism, or the shikimate pathway. The absence of flavonols in maize and Petunia could affect the accumulation of other compounds that are more specifically required for male fertility. Thus, differences between species in terms of flavonoid... 

Funk C, Brodelius P (1990c) Phenylpropanoid metabolism in suspension cultures of Vanilla planifolia Andr. Ill Conversion of 4-methoxycimnnamic acids into 4-hydroxybenzoic acids. Plant Physiol 94 102-108... 

Funk C, Brodelius P (1992) Phenylpropanoid metabolism in suspension cultures of Vanilla planifolia Andr. IV Induction of vanillinic acid formation. Plant Physiol 99 256-262 Funk C, Brodelius P (1994) Vanilla planifolia Andrews in vitro biosynthesis of vanillin and other phenylpropanoids derivatives. In Bajaj YPS (ed) Biotechnology in agriculture and forestry. Medicinal and aromatic plants VI, vol 26. Springer, Berlin Heidelberg New York, pp 377-402... 

The shikimate/arogenate pathway leads to the formation of three aromatic amino acids L-phenylalanine, L-tyrosine, and L-tryptophane. This amino acids are precursors of certain homones (auxins) and of several secondary compounds, including phenolics [6,7]. One shikimate/arogenate is thought to be located in chloroplasts in which the aromatic amino acids are produced mainly for protein biosynthesis, whereas the second is probably membrane associated in the cytosol, in which L-phenylalanine is also produced for the formation of the phenylpropanoids [7]. Once L-phenylalanine has been synthesized, the pathway called phenylalanine/hydroxycinnamate begins, this being defined as "general phenylpropanoid metabolism" [7]. 

The general phenylpropanoid pathway begins with the deamination of L-phenylalanine to cinnamic acid catalyzed by phenylalanine ammonia lyase (PAL), Fig. (1), the branch-point enzyme between primary (shikimate pathway) and secondary (phenylpropanoid) metabolism [5-7]. Due to the position of PAL at the entry point of phenylpropanoid metabolism, this enzyme has the potential to play a regulatory role in phenolic-compound production. The importance of this is illustrated by the high degree of regulation both during development as well as in response to environmental stimuli. 

Fig. (1). Schematic view of some branches of phenylpropanoid metabolism. Solid arrows indicate enzymatic reactions with the respective enzyme indicated on the right. PAL, phenylalanine ammonia-lyase C4H, cinnamate 4-hydroxylase 4CL, 4-coumarate CoA ligase CHS, chalcone synthase CF1, chalcone flavavone isomerase F3H, flavanone 3-hydroxylase DFR, dihydroflavonol reductase CHR, chalcone reductase. Broken arrows indicate metabolic branches towards several classes of phenylpropanoids, or several subsequent enzymatic steps. In some cases the enzymes indicated are also involved in other reactions, not shown.

Studies have shown that phenylpropanoid metabolism can be stimulated by ozone. The activity of PAL increased in soybean [91], Scots pine (Pinus sylvestris L.) [92], and parsley (Petroselinum crispum L.) [93] soon after treatment with 150-200 nmol O3 mol 1. Rapid increases in transcript levels for PAL in response to ozone have been observed in parsley [93], Arabidopsis thaliana L. Heynhold [94] and tobacco (Nicoticma tabacum L.) [95]. Transcript levels for 4-coumarate CoA ligase (4CL), the last enzyme in the general phenylpropanoid pathway, increased commensurately with PAL transcripts in ozone-treated parsley seedlings [93]. Phenolic compunds reported to accumulate in leaf tissue in response to ozone include hydroxycinnamic acids, salicylic acid, stilbenes, flavonoids, furanocoumarins, acetophenones, and proanthocyanidins [85, 92, 93, 96, 97]. 

These results, together with those of the other works described above indicate that phenylpropanoid metabolism may play an important role in the development of plant acclimation to thermal stress. 

With regard to the first point, most of the final enzymes of phenolic metabolism, that is, those that give rise to the formation of lignin, have not been characterized nor are their biochemical properties known, and therefore in the future it would be useful to elucidate these stages of phenylpropanoid metabolism. 

Ruegger, M., and Chappie, C., 2001, Mutations that reduce sinapoylmalate accumulation in Arabidopsis thaliana define loci with diverse roles in phenylpropanoid metabolism, Genetics 159 1741-1749. 

Hoffmann, L., Maury, S., Martz, F., Geoffroy, P., and Legrand, M., 2003, Purification, cloning, and properties of an acyltransferase controlling shikimate and quinate ester intermediates in phenylpropanoid metabolism, J. Biol. Chem 278 95-103. 

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