|Cote, Gregory - Greg|
Submitted to: The Federation of European Biochemical Societies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/1997
Publication Date: N/A
Citation: N/A Interpretive Summary: There is a need for mild, specific methods which create modified carbohydrates for adding value to farm products, particularly processed grain fractions. Certain commercially available enzymes are useful (environmentally benign or "green" technology) for making some modifications. However, most of the previous work has dealt with the use of enzymes that act on fats and proteins, rather than on carbohydrates. Taking advantage of a newly described class of enzymes that act specifically on carbohydrates, we have described their action. We found that they act differently from the previously used enzymes and present a new tool in the arsenal of methods for creating carbohydrate-based materials. This work will benefit specialty chemical producers, the paper industry, as well as chemists working on medically useful compounds. It will also help scientists understand the manner in which plant materials are broken down in nature, since the enzymes are involved in the breakdown of agricultural residues and wood pulp.
Technical Abstract: Substrate specificity of a purified acetylxylan esterase (AcXE) from Trichoderma reesei was investigated on partially and fully acetylated methyl glycopyranosides. The enzyme catalyzed deacetylation of methyl 2,3,4-tri-O-acetyl-beta-D-xylopyranoside at positions 2 and 3. A similar regioselectivity of deacetylation was initially observed with methyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside. The resulting methyl 4,6-di-O-acetyl-beta-D-glucopyranoside was further deacetylated, mainly to methyl 4-O-acetyl-beta-D-glucopyranoside. The second acetyl group is rapidly released from position 3 or 2 after the first acetyl group is removed from position 2 or 3. In acetylxylan degradation, the enzyme deacetylates monoacetylated xylopyranosyl residues more readily than doubly acetylated residues. The T. reesei AcXE does not appear to be specific for acetylxylan.