Biosynthesis of lignin

Biosynthesis of Lignin.—The mechanism of biosynthetic differentiation between the different lignins produced in gymnosperms and angiosperms has been explored by Shimada et al.f employing both enzymic and tracer procedures. The pathway of synthesis of the —C3 lignin precursors appears to 

The properties of the partly purified 0-methyltransferase from pine have also been studied. The enzyme shows a requirement for Mg, is inhibited by Co, Ni, Zn, and Cd, and has a maximal activity at pH 7.5. 0-Methyltransferase activity has also been examined in wheat plants, in relationship to growth and lignification. The enzyme activity reached two maxima, 6ne in 10-day-old plants and another at 28—30 days activity then fell off to a lower level. Enzyme activity was closely correlated with ferulic acid content in the wheat seedlings and the results indicate that there is a plentiful supply of precursor available before ligniflcation begins to take place. 

The three hydroxycinnamic acids, (16)—(18), undergo reduction to the corresponding alcohols before being incorporated into lignin. In spite of the 

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K. Freudenberg and A. C. Neish, The Constitution and Biosynthesis of Lignin, Springer-Verlag, Berlin (1968). 

Several groups have identified non-radioactive metabolic intermediates of lignification in cambial sap or sapwood extracts 54, 58 b, 68). The compounds detected agree well with the schemes for the biosynthesis of lignin precursors set forth in Figs. 1 and 2 and with the data described later for the third stretch of lignification. 

Freudenberg, K. In Constitution and Biosynthesis of Lignin Springer-Verlag Berlin, 1968 2, 45-122. 

The only stem materials examined were from the Setaria anceps and Digitaria decumbens grasses. The major substituted cyclobutane dimers in these walls appeared, from the mass spectral data, to be mixed dimers of ferulic acid and coniferyl alcohol (FA-ConAlc type). Further examination of the aromatics of stems is required but if such dimers are present then they may well be involved in the biosynthesis of lignin (41,42). 

Higuchi, T. Biosynthesis of Lignin. In Biosynthesis and Biodegradation of Wood Components Higuchi, T., Ed. Academic Press New York, 1985 pp. 141-60. 

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,... 

From a physiological standpoint, molecular and biochemical studies have suggested that ozone stimulates phenolic metabolism and the biosynthesis of lignin or other substances partly derived from coniferyl alcohol [89]. Lignification of mesophyll cell walls might confer some protection against oxidation, and thus be a defence response against ozone [90]. 

The wall material of plant cells is one of their distinguishing characteristics. As a result, lignin, cellulose, and other wall constituents have been studied in many plant tissue cultures. Phenylpropanoids. for example, have been shown lo be precursors of lignin formation in while pine. Set/noiii. lilac, rose, carrot, and geranium tissue cultures. Moreover, the biosynthesis of lignin has been shown to be alTeeted by kinetin. boron, and major elements, such as calcium. 

Goujon, T., Sibout, R., Eudes, A., MacKay, J., and Jouanin, L., 2003, Genes involved in the biosynthesis of lignin precursors in Arabidopsis thaliana, Plant Physiol. Biochem. 41 677-687. 

Higuchi, T., 1985, Biosynthesis of lignin, in Biosynthesis and Biodegradation of Wood Components, T. Higuchi, ed., Academic Press, Orlando, pp. 141-160. 

Freudenberg, K. Niesh, A.C. (1968). Constitution and biosynthesis of lignin. Molecular Biology, Biochemistry and Biophysics 2,132-9. New York Springer-Verlag. 

In the oxidative polymerization of phenols catalyzed by Cu complexes, the substrate coordinates to the Cu(II) complex and is then activated. The activated phenol couples in the next step. The Cu complex acts effectively as a catalyst at concentrations of 0.2-2 mol% compared to the substrate. The oxidation proceeds rapidly at room temperature under an air atmosphere to give poly(phenylene ether) in a quantitative yield. The polymerization follows Michaelis-Menten-type kinetics [55]. Enzymatic oxidation of phenols is an important pathway in the biosynthesis of lignin in plants [56] catalyzed by a metalloenzyme. 

Freudenberg K, Neish AC (1968) Constitution and biosynthesis of lignin Springer, Berlin Heidelberg New York, 64-77... 

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