Takayoshi Higuchi

Red-brown color of lignified tissues of transgenic plants with antisense CAD gene: Wine-red lignin from coniferyl aldehyde

Coniferyl aldehyde was converted to a wine-red lignin polymer with peroxidase/H2O2. Color of the lignin was very similar to that of lignified tissues of transgenic tobacco plants with an antisense gene of cinnamyl alcohol dehydrogenase (CAD; Schuch, 1993). Experimental results suggested that the red-brown color of lignified tissues of the transgenic plants is ascribed to the extendedly conjugated coniferyl aldehyde groups of abnormal lignin derived from dehydrogenative polymerization of coniferyl aldehyde. The result also showed that lignin content of the transgenic plants does not decrease but the red-brown lignin predominant with coniferyl aldehyde groups is easily digested by Kraft cooking in paper mills. The red-brown wood is expected to be used for furnitures without staining.

Purification and partial sequences of Aralia cordata cinnamyl alcohol dehydrogenase.

Cinnamyl alcohol dehydrogenase (CAD) (EC 1.1.1.195) from a dicot, Aralia cordata, was purified to homogeneity and its properties were characterized. The enzyme shows a preference for cinnamyl alcohols and cinnamyl aldehydes as substrates. The M(r) is estimated at 72,000. The enzyme is composed of two heterogeneous subunits of slightly different sizes, and it differs from the bean enzyme in the size of subunits. Partial amino acid sequencing of the purified enzyme was carried out both from the N-terminus and using selected peptides obtained by cyanogen bromide cleavage.

Comparative Study on Mild Depolymerization of Lignin Model Dehydrogenation Polymers and Milled Wood Lignin

Abstract Dehydrogenation polymers (DHPs) of coniferyl alcohol prepared in three different ways (bulk, end-wise and membrane) and spruce (Picea mariana) milled wood lignin (MWL) were depolymerized with dry hydrogen iodide. The amounts of the only monomeric product, 1,3-diiodo-1-(4-hydroxy-3-methoxyphenyl)propane and oligomeric products resulted from this procedure were compared. All DHPs differ noticeably from MWL in their structural organization, the bulk one being the best approximation. Yields of the diiodide were high in all cases (end-wise DHP: 45%, membrane DHP: 55%, MWL and bulk DHP: 20%). Molecular mass distributions of higher molecular mass products were similar in all the cases except end-wise DHP which demonstrated lesser degree of polymerization of high molecular mass fraction.