Lignin dehydrogenative polymerization mechanism: a poplar cell wall peroxidase directly oxidizes polymer lignin and produces in vitro dehydrogenative polymer rich in β‐O‐4 linkage

An investigation was performed to determine whether lignin dehydrogenative polymerization proceeds via radical mediation or direct oxidation by peroxidases. It was found that coniferyl alcohol radical transferred quickly to sinapyl alcohol. The transfer to syringaresinol was slower, however, the transfer to polymeric lignols occurred very slightly. This result suggests that the radical mediator theory does not sufficiently explain the mechanism for dehydrogenative polymerization of lignin. A cationic cell wall peroxidase (CWPO‐C) from poplar (Populus alba L.) callus showed a strong substrate preference for sinapyl alcohol and the sinapyl alcohol dimer, syringaresinol. Moreover, CWPO‐C was capable of oxidizing high‐molecular‐weight sinapyl alcohol polymers and ferrocytochrome c. Therefore, the CWPO‐C characteristics are important to produce polymer lignin. The results suggest that CWPO‐C may be a peroxidase isoenzyme responsible for the lignification of plant cell walls.

[1]  M. Gajhede,et al.  Differential activity and structure of highly similar peroxidases. Spectroscopic, crystallographic, and enzymatic analyses of lignifying Arabidopsis thaliana peroxidase A2 and horseradish peroxidase A2. , 2001, Biochemistry.

[2]  K. Sakai,et al.  Substrate-Specific Peroxidases in Woody Angiosperms and Gymnosperms Participate in Regulating the Dehydrogenative Polymerization of Syringyl and Guaiacyl Type Lignins , 1998 .

[3]  H. Wariishi,et al.  Direct interaction of lignin and lignin peroxidase from Phanerochaete chrysosporium. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[4]  Erich Adler,et al.  Lignin chemistry—past, present and future , 1977, Wood Science and Technology.

[5]  T. Oniki,et al.  Enhancement of Peroxidase-Dependent Oxidation of Sinapyl Alcohol by an Apoplastic Component, 4-Coumaric Acid Ester Isolated from Epicotyls of Vigna angularis L. , 1997 .

[6]  Hirofumi Hirai,et al.  Sinapyl alcohol-specific peroxidase isoenzyme catalyzes the formation of the dehydrogenative polymer from sinapyl alcohol , 2002, Journal of Wood Science.

[7]  K. Piontek,et al.  The crystal structure of lignin peroxidase at 1.70 A resolution reveals a hydroxy group on the cbeta of tryptophan 171: a novel radical site formed during the redox cycle. , 1999, Journal of molecular biology.

[8]  O. Mattsson,et al.  Arabidopsis ATP A2 peroxidase. Expression and high-resolution structure of a plant peroxidase with implications for lignification , 2000, Plant Molecular Biology.

[9]  G. Brunow,et al.  Regioselectivity in lignin biosynthesis. The influence of dimerization and cross-coupling , 2000 .

[10]  T. Nishida,et al.  Treatment of poplar callus with ferulic and sinapic acids I: incorporation and enhancement of lignin biosynthesis , 2003, Journal of Wood Science.

[11]  W. Vermerris,et al.  Lignin formation in plants. The dilemma of linkage specificity. , 2001, Plant physiology.

[12]  Karl Freudenberg,et al.  Constitution and Biosynthesis of Lignin , 1968 .

[13]  J. Ralph,et al.  Facile large-scale synthesis of coniferyl, sinapyl, and p-coumaryl alcohol , 1992 .

[14]  K. Piontek,et al.  Crystal structures of pristine and oxidatively processed lignin peroxidase expressed in Escherichia coli and of the W171F variant that eliminates the redox active tryptophan 171. Implications for the reaction mechanism. , 2001, Journal of molecular biology.

[15]  M. Miller,et al.  Regulation of interprotein electron transfer by Trp 191 of cytochrome c peroxidase. , 1995, Biochemistry.

[16]  H. Wariishi,et al.  Oxidation of ferrocytochrome c by lignin peroxidase. , 1994, Biochemistry.

[17]  U. Takahama,et al.  Oxidation of hydroxycinnamic acid and hydroxycinnamyl alcohol derivatives by laccase and peroxidase. Interactions among p-hydroxyphenyl, guaiacyl and syringyl groups during the oxidation reactions , 1995 .

[18]  M. Gold,et al.  Lignin peroxidase oxidation of veratryl alcohol: effects of the mutants H82A, Q222A, W171A, and F267L. , 2002, Biochemistry.

[19]  G. Brunow,et al.  Oxidative cross coupling of p-hydroxycinnamic alcohols with dimeric arylglycerol β-aryl ether lignin model compounds. The effect of oxidation potentials , 1998 .