|Biely, Peter - SLOVAK ACAD OF SCIENCES|
|Kremnicky, Lubomir - SLOVAK ACAD OF SCIENCES|
|Tenkanen, M - VTT BIOTECHNOL & FOOD RES|
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.