Phenylpropanoids characterization

Stilbenes are a small group of phenylpropanoids characterized by a 1,2-diphenylethylene backbone. Most plant stilbenes have phytoalexin activity and are mainly derivatives of the monomeric unit frans-resveratrol (trans-R, 3,4, 5-trihydroxystilbene) although other stilbene structures are found in plants. 

The 4-coumarate CoA ligase (4CL EC 6.2.1.12) enzyme activates 4-coumaric acid, caffeic acid, ferrulic acid, and (in some cases) sinapic acid by the formation of CoA esters that serve as branch-point metabolites between the phenylpropanoid pathway and the synthesis of secondary metabolites [46, 47]. The reaction has an absolute requirement for Mg " and ATP as cofactors. Multiple isozymes are present in all plants where it has been studied, some of which have variable substrate specificities consistent with a potential role in controlling accumulation of secondary metabolite end-products. Examination of a navel orange EST database (CitEST) for flavonoid biosynthetic genes resulted in the identification of 10 tentative consensus sequences that potentially represent a multi-enzyme family [29]. Eurther biochemical characterization will be necessary to establish whether these genes have 4CL activity and, if so, whether preferential substrate usage is observed. 

Gauthier, A., Gulick, P.J., and Ibrahim, R.K., Characterization of two cDNA clones which encode 0-methyltransferases for the methylation of both fiavonoid and phenylpropanoid compounds. 

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. 

Deluc L, Barrieu F, Marchive C, Lauvergeat V, Decendit A, Richard T, Carde JP, Merillon JM, Hamdi S. 2006. Characterization of a grapevine R2R3-MYB transcription factor that regulates the phenylpropanoid pathway. Plant Physiol 140 499-511. 

Unlike most structurally characterized methyltransferases of non-plant origin that are monomeric, ChOMT forms a symmetric homodimer.21 Dimerization appears to be critical for activity in vitro as well as in vivo. The presence of a dimerization interface appears to be common to plant OMTs, and in this family of OMTs this homotypic protein-protein interface intimately contributes to substrate binding. Because of the broad structural diversity of phenylpropanoid compounds, ChOMT, like many plant OMTs, possesses highly selective substrate and positional specificity. Efficient substrate discrimination and binding is achieved through shape... 

From a biogenetic standpoint, capsaicin is an acylated degraded phenylpropanoid. Both its aromatic and its acyl moiety are the result of unique metabolic processes that, though simple in principle, are still poorly characterized in terms of enzymology and regulation. Since vanillamine (23) is abundant in placental tissues of Capsicum, the only site of biosynthesis of capsaicinoids, the limiting factor for the synthesis of... 

Comino, C., Lanteri, S., Portis, E., Acquadro, A., Romani, A., Hehn, A., Larbat, R. and Bourgaud, R (2007) Isolation and functional characterization of a cDNA coding a hydroxycinnamoyltransferase involved in phenylpropanoid biosynthesis in Cynara cardunculus L. BMC Plant Biol, 7. 

PAL and TAL are apparently represented to a very limited extent in bacteria, this presumably accounting for the general paucity of phenylpropanoids in such organisms. Isolation and characterization of PALs have, however, been described for R. toruloides Streptomyces maritimus Photorhabdus luminescens Sorangium cdlulosum, and Streptomyces verticillatus with the -cinnamic acid (3) so-formed being considered, for... 

S. Hamdi Characterization of a grapevine R2R3-MYB transcription factor that regulates the phenylpropanoid pathway Plant Physiol. 140 (2006) 499-511. 

Essential oils are volatile compounds responsible for the aromas commonly associated with many plants (see essay "Terpenes and Phenylpropanoids")- The chief constituent of the essential oil from cloves is aromatic and volatile with steam. In this experiment, you will isolate the main component derived from this spice by steam distillation. Steam distillation provides a means of isolating natural products, such as essential oils, without the risk of decomposing them thermally. Identification and characterization of this essential oil will be accomplished by infrared spectroscopy. 

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