Hydroxyferulic acid

Zhang, FI., Wang, J., and Goodman, H.M., An Arabidopsis gene encoding a putative 14-3-3-interacting protein, caffeic acid/5-hydroxyferulic acid 0-methyltransferase. Biochim. Biophys. Acta, 1353, 199, 1997. 

There are six common cinnamic acids, which have a C6 - C3 skeleton. All plants probably contain at least three of them. Shown below are cinnamic, acid (1.12), / -coumanc acid (1.13), caffeic acid (1.14), ferulic acid (1.15), 5-hydroxyferulic acid (1.16), and sinapic acid (1.17). 

As discussed in Section 7, the general phenylpropanoid pathway originally included the biosynthesis of the hydroxycinnamic acids caffeic acid (3.32), femlic acid (3.33), 5-hydroxyferulic acid (3.34), and sinapic acid (3.35) from />coumaric acid (3.30), as well as the corresponding CoA-esters... 

Figure 1.35 Schematic diagram of the phenolic biosynthetic pathway accompanied by the key enzymes involved. Enzyme abbreviations PAL, phenylalanine ammonia-lyase BA2H, benzoic acid 2-hydroxylase C4H, cinnamate 4-hydroxylase COMT-1, caffeic/5-hydroxyferulic acid O-methy I transferase 4CL, p-co um a ra te C o A ligase F5H, ferulate 5-hydroxylase GT, galloyltransferase ACoAC, acetylCoA carboxylase.

Caffeic Acid / 5-Hydroxyferulic Acid 3/5-O-Methyltransferase (COMT) 46... 

ZUBIETA, C., KOTA, P., FERRER, J.-L., DIXON, R.A., NOEL, J.P., Structural basis for the modulation of lignin monomer methylation by caffeic acid / 5-hydroxyferulic acid 3/5-O-methyltransferase, Plant Cell, 2002, 14, 1265-1277. 

MAURY, S., GEOFFROY, P., LEGRAND, M., Tobacco O-methyltransferases involved in phenylpropanoid metabolism. The different caffeoyl-coenzyme A/5-hydroxyferuloyl-coenzyme A 3/5-O-methy (transferase and caffeic acid/5-hydroxyferulic acid 3/5-O-methyltransferase classes have distinct substrate specificities and expression patterns., Plant Physiol., 1999,121,215-223. 

COMT (EC 2.1.1.68) was detected as an enzyme methylating caffeic acid to ferulic acid with the help of SAM and later it was shown that 5-hydroxyferulic acid is also methylated to sinapic acid. Mostly, other substrates will be accepted as well (Roje, 2006). Nowadays, however, there are strong indications that the hydroxycinnamic aldehydes and/or alcohols will be preferentially methylated by COMTs (Parvathi et al, 2001). Kinetic investigations of the... 

Eckardt, N.A. (2002) Probing the mysteries of lignin biosynthesis The crystal structure of caffeic acid/5-hydroxyferulic acid 3/5-O-methyltransferase provides new insights. Plant Cell, 14,1185-9. 

M., Leple, J.-C., Pilate, G., Cornu, D., Monties, B., Van Montagu, M., Inze, D., Boerjan, W., and Jouanin, L. (1995) A novel lignin in poplar trees with a reduced caffeic acid/5-hydroxyferulic acid 0-methyltransferase activity. Plant J. 8(6), 855-864. 

Ferulate 5-hydroxylase (F5H) catalyzes the third P-450 hydroxylation step at the C5 position of the phenolic ring to ultimately afford, via the monolignol pathway, 5-hydroxyconiferyl (22) and/or sinapyl (23) alcohols. This P-450 was first detected in xylem and sclerenchyma-enriched tissues from poplar Populus x euramericana), with microsomal extracts able to catalyze hydroxylation of ferulic acid (6) to 5-hydroxyferulic acid (7) in the presence of NADPH with apparent values of 6.3 pmoll / This enzyme was thus characterized as F5H. 

Propenoic acid, 3-(4,5-dihydroxy-3-methoxyphenyl)- 5-hydroxyferulic acid 1102 ... 

Figure 3.1 Primary flux of carbon through phenylpropanoid pathway in Arabidopsis. PAL, phenylalanine ammonia-lyase 4CL, 4-(hydroxy)cinnamoyl CoA ligase C4H, cinnamate 4-hydroxylase HCT, hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyltransferase C3 H, /7-coumaroylshikimate 3 -hydroxylase CCoAOMT, caffeoyl CoA O-methyltransferase F5H, ferulate 5-hydroxylase COMT, caffeic acid/5-hydroxyferulic acid o-methyltransferase CCR, cinnamoyl CoA reductase CAD, cinnamyl alcohol dehydrogenase. Not depicted is the HCT catalyzed synthesis of/r-coumaroyl quinate.

Higher plants accumulate a wide range of phenolic compounds that are derivatives or metabolites of cinnamic acid. The phenyl-propanes, generally denoted as C -C compounds, are important intermediates in the biosynthesis of lignin and flavonoids. The common phenylpropane derivatives cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, 5-hydroxyferulic acid, and sinapic acid, are interrelated and are synthesized from phenylalanine (Fig. 5). 

Tyrosine p-Coumaric add Cafieicadd Feiulicadd 5-Hydroxyferulic acid Sinapicacid... 

Other cinnamic acids also produce aldehydes, but they have no significance as odour-active substances. By analogy, coumaralde-hyde is produced from 4-coumaric acid, caffeoyl aldehyde from caffeic acid, conifer aldehyde (also known as ferulyl aldehyde) from ferulic acid, 5-hydroxyconifer aldehyde from 5-hydroxyferulic acid and sinapyl aldehyde from sinapic acid. These aldehydes can be reduced to the corresponding alcohols, with which they play a role as the building units of lignin biosynthesis. 

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