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United States Department of Agriculture

Agricultural Research Service

Title: A Study of the Mechanism of Action of Acetylxylan Esterase from Trichoderma Reesei on Acetylated Methyl Glycosides

item Cote, Gregory
item Kremnicky, Lubomir - SLOVAK ACAD OF SCIENCES
item Tenkanen, M - VTT BIOTECHNOL & FOOD RES
item Greene, Richard

Submitted to: International Triticeae Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: April 17, 1997
Publication Date: N/A

Technical Abstract: Substrate specificity of purified acetylxylan esterase (AcXE) from Trichoderma reesei was investigated on partially and fully acetylated methyl glycopyranosides. The enzyme catalyzed double deacetylation of methyl 2,3,4-tri-O-acetyl-beta-D-xylopyranoside at positions 2 and 3 yielding methyl 4-O-acetyl-beta-D-xylopyranoside in almost 90% yield. A similar regioselectivity of deacetylation was initially observed with methyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside, however, the resulting methyl 4,6-di-O-acetyl-beta-D-glucopyranoside was a subject of further deacetylation mainly to methyl 4-O-acetyl-beta-D- glucopyranoside and partially to 6-O-acetyl-beta-D-glucopyranoside. Of the three methyl xylopyranoside diacetates, the 2,3-diacetate was deactylated by the enzyme at a similar rate as the fully acetylated derivative. The other two diacetates, 2,4- and 3,4-, i.e. the compounds which have a free hydroxyl group at position 2 or 3, were deacetylated also to methyl 4-O-acetyl-beta-D-xylopyranoside, however, one order of magnitude faster than methyl 2,3,4-tri-O-acetyl-beta-D- xylopyranoside and methyl 2,3-di-O-acetyl-beta-D-xylopyranoside. These findings explain the observed double deacetylation of fully acetylated methyl xylopyranoside. The second acetyl group is released from positions 3 or 2 much easier after the first acetyl group is removed.

Last Modified: 4/21/2015
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