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Mechanism of action of the endo ‐(1 → 3)‐α‐glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum
Author(s) -
Grün Christian H.,
Dekker Nick,
Nieuwland Alexander A.,
Klis Frans M.,
Kamerling Johannis P.,
Vliegenthart Johannes F.G.,
Hochstenbach Frans
Publication year - 2006
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2006.05.062
Subject(s) - glycosidic bond , trichoderma harzianum , trisaccharide , glucanase , glucan , hydrolysis , stereochemistry , anomer , laminarin , cell wall , chemistry , hypocrea , glycoside hydrolase , tetrasaccharide , biochemistry , polysaccharide , enzyme , biology , botany , cellulase , trichoderma reesei , biological pest control
(1 → 3)‐α‐Glucanases catalyze the hydrolysis of fungal cell wall (1 → 3)‐α‐glucan, and function during cell division of yeasts containing this cell wall component or act in mycoparasitic processes. Here, we characterize the mechanism of action of the (1 → 3)‐α‐glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum . We observed that MutAp releases predominantly β‐glucose upon hydrolysis of crystalline (1 → 3)‐α‐glucan, indicating inversion of the anomeric configuration. After having identified (1 → 3)‐α‐glucan tetrasaccharide as the minimal substrate for MutAp, we showed that reduced (1 → 3)‐α‐glucan pentasaccharide is cleaved into a trisaccharide and a reduced disaccharide, demonstrating that MutAp displays endo ‐hydrolytic activity. We propose a model for the catalytic mechanism of MutAp, whereby the enzyme breaks an intrachain glycosidic linkage of (1 → 3)‐α‐glucan, and then continues its hydrolysis towards the non‐reducing end by releasing β‐glucose residues in a processive manner.