P-coumarate-3-hydroxylase

L-Phenylalanine,which is derived via the shikimic acid pathway,is an important precursor for aromatic aroma components. This amino acid can be transformed into phe-nylpyruvate by transamination and by subsequent decarboxylation to 2-phenylacetyl-CoA in an analogous reaction as discussed for leucine and valine. 2-Phenylacetyl-CoA is converted into esters of a variety of alcohols or reduced to 2-phenylethanol and transformed into 2-phenyl-ethyl esters. The end products of phenylalanine catabolism are fumaric acid and acetoacetate which are further metabolized by the TCA-cycle. Phenylalanine ammonia lyase converts the amino acid into cinnamic acid, the key intermediate of phenylpropanoid metabolism. By a series of enzymes (cinnamate-4-hydroxylase, p-coumarate 3-hydroxylase, catechol O-methyltransferase and ferulate 5-hydroxylase) cinnamic acid is transformed into p-couma-ric-, caffeic-, ferulic-, 5-hydroxyferulic- and sinapic acids,which act as precursors for flavor components and are important intermediates in the biosynthesis of fla-vonoides, lignins, etc. Reduction of cinnamic acids to aldehydes and alcohols by cinnamoyl-CoA NADPH-oxido-reductase and cinnamoyl-alcohol-dehydrogenase form important flavor compounds such as cinnamic aldehyde, cin-namyl alcohol and esters. Further reduction of cinnamyl alcohols lead to propenyl- and allylphenols such as... 

HAL and PAL Proposed Tyr loop-in model for breathing motion tor substrate access The molecular basis of PAL and TAL substrate versatility Hydroxycinnamoyl CoA Shikimate/Quinate Hydroxycinnamoyltransferase Cytochrome P-450 Hydroxylation Reactions (Cinnamate 4-Hydroxylase, p-Coumarate 3-Hydroxylase , and Ferulate 5-Hydroxylase ) Comparison to Bacterial/Mammalian P-450s Subcellular localization of C4H, pC3H , and F5H ... 

Cinnamate 4-hydroxylase p-Coumarate 3-hydroxylase Ferulate 5-hydroxylase... 

L. B. Davin N. G. Lewis, Reaction tissue formation and stem tensile modulus properties in wild type and p-coumarate-3-hydroxylase downregulated lines of alfalfa, Medicago sativa (Fabaceae), pp 912-925, Copyright 2007, with permission from the Botanical Society of America (g). 

Figure 4 Current view of the phenylpropanoid pathway to the monolignols 19-23. 4CL, 4-hydroxycinnamate coenzyme Aligases pC3H , p-coumarate 3-hydroxylase C4H, cinnamate 4-hydroxylase CAD, cinnamyl alcohol dehydrogenases CCOMT, hydroxycinnamoyl CoA O-methyltransferases CCR, cinnamoyl-CoA oxidoreductases COMT, caffeic acid O-methyltransferases F5H , ferulate 5-hydroxylase HCT, hydroxycinnamoyl-CoA shikimate hydroxycinnamoyltransferase HOT, hydroxycinnamoyl-CoA quinate hydroxycinnamoyltransferase PAL, phenylalanine ammonia lyase TAL, tyrosine ammonia lyase.

Cytochrome P-450 Hydroxylation Reactions (Cinnamate 4-Hydroxylase, p-Coumarate 3-Hydroxylase , and Ferulate 5-Hydroxylase ) Comparison to Bacterial/ Mammalian P-450s... 

Figure 1. Proposed biosynthetic pathway to monolignols, and related metabolites, a. Phenylalanine ammonia-lyase, b. Tyrosine ammonia-lyase, c. Cinnamate-4-hydroxylase, d. p-Coumarate-3-hydroxylase, e. O-Methyltransferase, f. Ferulate-5-hydroxylase, g. Hydroxycinnamate-CoA ligase, h. Cinnamoyl-CoA NADP oxidoreductase, i. Cinnamyl alcohol dehydrogenase. ( Note plus acetate pathway for both flavonoids and suberin)...

Figure 1.37 Proposed biosynthetic pathway of curcuminoids in tumeric. Enzyme abbreviations CCOMT, caffeoyl-CoA O-methyltransferase 4CL, 4-coumarate CoA ligase CST, shikimate transferase CS3 H, p-coumaroyl 5-O-shikimate 3 -hydroxylase OMT, O-methyltransferase PKS, polyketide synthase. [Adapted from Ramirez-Ahumada et al. (2006)]...

Phenylalanine ammonia-lyase (PAL) eliminates the amino group from phenylalanine (12) to produce cinnamic acid (13). Cinnamate-4-hydroxylase (C4H) hydroxidizes compound (13) to yield p-coumaric acid (14). 4-CoumaroyhCoA-ligase (4CL) complex catalyzed the conversion of p-coumaric acid (14) and coenzyme A (CoA) to 4-coumaroyl-CoA (15) and 3 moles malonyl-CoA (16). Stilbene synthase (STS) converts these two compounds (15,16) into resveratrol of stilbene (7) (Fig. 3) [23,24],... 

Fig, 5.2. Biosynthesis of flavonoids and proanthocyanidins (condensed tannins). Enzymes in bold have been cloned from P. tremuloides and show induction by herbivory (Peters and Constabel, 2002 R. Mellway and C. P. Constabel, unpublished data). Abbreviations are as follows Phe, phenylalanine PAL, phenylalanine ammonia lyase 4CL, 4-coumarate CoA Ligase CHS, chalcone synthase CHI, chalcone isomerase F3H, flavanone 3-hydroxylase FLS, flavonol synthase DFR,... 

Some relatively nonspecific enzymatic formation of caffeic (12), ferulic (13), and synapic (14) acids has been noted (Davin et al., 1992). Monooxygenases of microsomal fractions appear to be involved. For example, a specific p-coum-arate-3-hydroxylase has been isolated from mung beans. However, other work suggests that the carboxyl group of p-coumaric acid must be esterified as a quinic acid ester before... 

An alternate fate of the products of photosynthesis that are channeled through the shikimate pathway is for 3-dehydroshikitnic acid to be directed to L-phenylalanine and so enter the phenylpropanoid pathway (Figure 1.15). Phenylalanine ammonia-lyase catalyses the first step in this pathway, the conversion of L-phenylalanine to cinnamic acid, which in a reaction catalysed by cinnamate 4-hydroxylase is converted to p-coumaric acid which in turn is metabolized to p-coumaroyl-CoA by p-coumarate CoA ligase. Cinnamic add is... 

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