Biosynthesis lignin

Quinone methides have been shown to be important intermediates in chemical synthesis,1 2 in lignin biosynthesis,3 and in the activity of antitumor and antibiotic agents.4 They react with many biologically relevant nucleophiles including alcohols,1 thiols,5-7 nucleic acids,8-10 proteins,6 11 and phosphodiesters.12 The reaction of nucleophiles with ortho- and /iara-quinone methides is pH dependent and can occur via either acid-catalyzed or uncatalyzed pathways.13-17 The electron transfer chemistry that is typical of the related quinones does not appear to play a role in the nucleophilic reactivity of QMs.18... 

Boerjan, W. Ralph, J. Baucher, M. Lignin biosynthesis. Annu. Rev. Plant Biol. 2003,54, 519-549. 

Brunow, G. Karlsson, O. Lundquist, K Sipila, J. On the distribution of the diaster-eomers of the structural elements in lignins the steric course of reactions mimicking lignin biosynthesis. Wood Sci. Technol. 1993, 27, 281-286. 

Karhunen, P Rummakko, P. Sipila, J. Brunow, G. Kilpelainen, I. The formation of dibenzodioxocin structures by oxidative coupling. A model reaction for lignin biosynthesis. Tetrahedron Lett. 1995, 36, 4501 4504. 

Onnerud, H. Zhang, L. Gellerstedt, G. Henriksson, G. Polymerization of monolignols by redox shuttle-mediated enzymatic oxidation a new model in lignin biosynthesis I. Plant Cell 2002, 14, 1953-1962. 

WHETTEN, R., SEDEROFF, R., Lignin biosynthesis, Plant Cell, 1995, 7,1001-1013. 

Biotin metabolism Folate biosynthesis One carbon pool by folate Retinol metabolism Porphyrin and chlorophyll metabolism Terpenoid biosynthesis Xenobiotics metabolism Ubiquinone biosynthesis Flavonoids, stilbene, and lignin biosynthesis... 

El-Basyouni, S.Z., A. C. Neish, andG. H. N. Towers The Phenolic Acids in Wlxeat III. Insoluble Derivatives of Phenolic Cinnamic Acids as Natural Intermediates in Lignin Biosynthesis. Phytochem. 3, 627—640 (1964). 

Figure 49 The precursors of lignin biosynthesis, p-coumaryl alcohol (I), coniferyl alcohol (II) and sinapyl alcohol (III). [65]...

Validation of the role of femloyl-CoA in the synthesis of the vanillin precursor will be detection of the appropriate intermediates and/or enzyme activities in placental extracts that could account for the production of the predicted levels of capsaicinoids. The presence of low levels of monolignol intermediates could be explained by lignin biosynthesis. An alternate route from phenylalanine to vanillin has been considered by some investigators Orlova et al. [68] demonstrated the role of the benzenoid pathway in petunia flowers for the biosynthesis of phenylpropanoid/benzenoid volatiles. 

Boerjan W, Ralph J, Baucher M (2003) Lignin biosynthesis. Annu Rev Plant Biol 54 519-546 Dixon RA, Reddy MSS (2003) Biosynthesis of monolignols. Genomic and reverse genetic approaches. Phytochem Rev 2 289-306... 

Noguchi et al. (8) synthesized precursors of lignin biosynthesis (i.e., coniferyl and sinapyl alcohols) in which the side chain and methoxy groups were doubly labeled by and H, prepared the DHP (synthetic lignin) from them, and treated the DHP with the laccase. These results showed that about 25% of Hs of the a- and -positions were removed in a ratio of one to one, respectively, and that the methoxyl group of a syringyl unit was de-methylated easier than that of a guaiacyl. 

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

Two main anionic groups were present in the xylem and their activity towards ferulic salts and their fluorinated analogues was determined. Whether the two isozymes represent enzymes specifically involved in lignin biosynthesis is discussed. 

Induced lignification is blocked by treatments which inhibit protein synthesis (10), and it seems likely therefore that the increases in activities observed for enzymes involved in lignin biosynthesis (7,8) depend on enhanced translation, and probably enhanced transcription of the appropriate genes, as has been shown for the phytoalexin response of some plants (27). However, the molecular biology of the response in wheat awaits investigation. 

Lignin Biosynthesis in Stem Rust Infected Wheat... 

A different approach to investigate active lignification during resistance reactions is provided by the determination of enzyme activities involved in lignin biosynthesis. Resistant plants are expected to be more strongly activated during or immediately preceding the resistance reaction compared to susceptible plants. Thus, phenylalanine ammonia-lyase (PAL) (43-45), cinnamic acid 4-hydroxylase (46), O-methyltransferases (44), and... 

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). 

Tiburzy (22,31) obtained similar results by application of the PAL inhibitor aminooxyacetic acid (AOA). However, AOA does not specifically inhibit PAL (99), and PAL is not only involved in lignin biosynthesis (100). Thus, AOA and the related inhibitor aminooxyphenyl propionic acid (AOPP) (101,102) inhibit the biosynthesis of lignin (103,104), anthocyanins (105), other flavonoids (106), and conjugates of cinnamic acids (107) via PAL, as well as ethylene (108-110) via a pyridoxal phosphate dependent enzyme (110,111). In view of the possible function of phenolic compounds as phytoalexins (21,112,113) and the well documented role of ethylene in some resistance reactions (114-116), the above cited experiments with AOA (22,... 

Table I. Comparison of Lignin Biosynthesis and Biodegradation Mechanisms...

---