Submitted to: International Symposium on Wood and Pulping Chemistry
Publication Type: Proceedings
Publication Acceptance Date: 2/28/2003
Publication Date: 6/1/2003
Citation: LU, F., RALPH, J., MARITA, J.M., LAPIERRE, C., JOUANIN, L., BOERJAN, W. SEQUENCING AROUND 5-HYDROXYCONIFERYL ALCOHOL-DERIVED UNITS IN COMT-DEFICIENT LIGNINS. INTERNATIONAL SYMPOSIUM ON WOOD AND PULPING CHEMISTRY. 2003. Interpretive Summary:
Technical Abstract: COMT is a bifunctional lignin-biosynthetic-pathway enzyme that methylates 5-hydroxy and 3-hydroxy positions on the aromatic ring with preference for 5-hydroxyconiferaldehyde on the way to produce the monolignol sinapyl alcohol. Lignins in COMT-deficient plants contain benzodioxane substructures due to incorporation of 5-hydoxyconiferyl alcohol (5-OH-CA). The DFRC method can be used to detect and determine benzodioxane structures because of their total survival in this degradation. Moreover, a partial sequence of 5-OH-CA incorporation in lignin can be derived from detection or isolation and structural analysis of the benzodioxane products. Results from DFRC analysis of COMT deficient lignins provide evidence that 5-OH-CA cross-couples (at its b-position) with syringyl or guaiacyl units (at their O'4-positions) into the growing lignin polymer and then either coniferyl or sinapyl alcohol adds to the 5-hydroxyguaiacyl terminus producing the benzodioxane. This new terminus may also become etherified by coupling with further monolignols, intimately incorporating the 5-OH-CA into the lignin structure.