Stereochemistry of the hydrolysis of glycosidic linkage by endo-beta-1,4-xylanases of Trichoderma reesei.
Methyl beta-D-xylotrioside was used as a non-reducing substrate to investigate the stereochemistry of hydrolysis of beta-1,4-xylopyranosidic linkage by purified endo-beta-1,4-xylanases (EC 3.2.1.8) of Trichoderma reesei, employing 1H NMR spectroscopy. The fungus produces one acidic species (pI 4.8-5.5), designated as EXI, and one alkaline species (pI 8.5-9.0), designated as EXII. Both enzymes were found to cleave the xylotrioside predominantly to methyl beta-D-xyloside and xylobiose. Monitoring of the intensity of the H-1 signals of alpha- and beta-xylobiose during the time course of hydrolysis clearly showed that both enzymes liberate the beta-anomer of xylobiose, i.e. a product with anomeric configuration identical with that of the cleaved glycosidic linkage. This means that both EXI and EXII belong to the so-called retaining glycanases that utilize the double displacement reaction mechanism of hydrolysis.
Biely
P
P
Institute of Chemistry, Slovak Academy of Sciences, Bratislava.
Kremnický
L
L
Alföldi
J
J
Tenkanen
M
M
D043364:Endo-1,4-beta Xylanases; D006027:Glycosides / Q000378:metabolism*; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D014242:Trichoderma / Q000201:enzymology*; D014990:Xylans / Q000737:chemistry / Q000378:metabolism; D014995:Xylosidases / Q000378:metabolism*
D006027:Glycosides; D014990:Xylans; D014995:Xylosidases; D043364:Endo-1,4-beta Xylanases