Lignin biosynthesis studies

Table I. Use of Doubly labeled Guaiacyl Lignin Precursors in Lignin Biosynthesis Studies...

Hydrogenolysis has also found use in a lignin biosynthesis study in which 14C-labeled lignin precursors were administered to wheat plants and maple twigs and ultimately recovered in the form of the typical lignin hydrogenolysis products, dihydroconiferyl and dihydrosinapyl alcohols (Brown and Neish 1959). 

Karkonen, A., Koutaniemi, S. Lignin biosynthesis studies in plant tissue cultures. J. Integrative Plant Biol 52(2), 176-185 (2010)... 

In a recent study (54), we showed increased activities of two enzymes of the general phenylpropanoid pathway, PAL and 4-coumarate CoA lig-ase, as well as one enzyme of the specific pathway of lignin biosynthesis, cinnamy 1-alcohol dehydrogenase (CAD), in resistant plants at the time of the hypersensitive host cell death. On the other hand, decreased activities were observed at the same time with susceptible host plants (54). Furthermore, we showed that the well known increase in peroxidase activities, which is strong in resistant and only weak in susceptible plants (55-58), is at least partly due to the increased activity of the lignin biosynthetic pathway (54,59). 

Brunow G, Sipila J, Makela T (1989) On the mechanism of formation of non-cyclic benzyl ethers during lignin biosynthesis Holzforschung 43 55-59 Ede RM, Brunow G, Simola LK, Lemmetyinen J (1990) Two-dimensional H- H chemical shift correlation and J-resolved NMR studies on isolated and synthetic lignins Holzforschung 44 95-101... 

Brown SA, Neish AC (1959) Studies of lignin biosynthesis using isotopic carbon VIII Isolation of radioactive hydrogenolysis products of lignin J Am Chem Soc 81 2419-2424... 

Laccases are so widely distributed in the fungi that it is very possible that this enzyme may be ubiquitous in these organisms [3,116], Laccases have also been found in a large variety of plant species [117], in about a dozen studied insects [118], and has also recently been found in the hacterium Azospirillum lipoferum [119]. Laccase has a variety of functions including participation in lignin biosynthesis [117], degradation of plant cell-walls [120,121], plant pathogenicity [122], and insect sclerotiza-tion [123]. 

In early studies on lignin biosynthesis prepared a lignin like polymer was prepared in vitro, named dehydrogenation polymer (DHP) [46]. Authors concluded that lignin was produced by the random diffusion of monomeric building blocks... 

Weng, J.K., Banks, J.A., Chappie, C. Parallels in lignin biosynthesis a study in Selaginella moellendorffii reveals convergence across 400 million years of evolution. Commun. Integr. Biol. 1, 20-22 (2008)... 

Capsaicinoids are synthesized by the condensation of vanillylamine with a short chain branched fatty acyl CoA. A schematic of this pathway is presented in Fig. 8.4. Evidence to support this pathway includes radiotracer studies, determination of enzyme activities, and the abundance of intermediates as a function of fruit development [51, 52, 57-63], Differential expression approaches have been used to isolate cDNA forms of biosynthetic genes [64-66], As this approach worked to corroborate several steps on the pathway, Mazourek et al. [67] used Arabidopsis sequences to design primers to clone the missing steps from a cDNA library. They have expanded the schema to include the biosynthesis of the key precursors phenylalanine and leucine, valine and isoleucine. Prior to this study it was not clear how the vanillin was produced, and thus the identification of candidate transcripts on the lignin pathway for the conversion of coumarate to feruloyl-CoA and the subsequent conversion to vanillin provide key tools to further test this proposed pathway. 

The functions of phenylpropanoid derivatives are as diverse as their structural variations. Phenylpropanoids serve as phytoalexins, UV protectants, insect repellents, flower pigments, and signal molecules for plant-microbe interactions. They also function as polymeric constituents of support and surface structures such as lignins and suberins [1]. Therefore, biosynthesis of phenylpropanoids has received much interest in relation to these functions. In addition, the biosynthesis of these compounds has been intensively studied because they are often chiral, and naturally occurring samples of these compounds are usually optically active. Elucidation of these enantioselective mechanisms may contribute to the development of novel biomimetic systems for enantioselective organic synthesis. 

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