Monomeric phenylpropanoids

There are at least five types of phenylpropanoid related reactions which appear to occur in plant cell walls. Two are UV-mediated photochemical reactions, and hence may be restricted only to the first few layers of cells under the plant surface due to poor penetrability of the light (3). The other reactions appear to be enzymatically mediated, and result in the formation of dimers or polymers from the corresponding monomeric units. 

If, as a criterion of value to the study of lignin depolymerization by alkaline hydrolysis, the maximum yield of oxygen-bearing, phenylpropanoid derivatives is chosen, then the conditions of such a study have been optimized here at a treatment severity corresponding to a reaction temperature of 300°C for 1 hour. Under these conditions, 20% of the lignin is recovered as ether-solubles of which 55% is identifiable as monomeric derivatives. The rest of this material probably consists of dimeric-type compounds not identified by capillary gas chromatography. 

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... 

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. 

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