Mechanism of action of the endo-(1-->3)-alpha-glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum.

Christian H Grün, Nick Dekker, Alexander A Nieuwland, Frans M Klis, Johannis P Kamerling, Johannes F G Vliegenthart, Frans Hochstenbach

Bijvoet Center, Department of Bio-Organic Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.

FEBS letters 2006 Jul 10

filter terms:

1-->3)-alpha-glucanases catalyze the hydrolysis of fungal cell wall (1-->3)-alpha-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)-alpha-glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum. We observed that MutAp releases predominantly beta-glucose upon hydrolysis of crystalline (1-->3)-alpha-glucan, indicating inversion of the anomeric configuration. After having identified (1-->3)-alpha-glucan tetrasaccharide as the minimal substrate for MutAp, we showed that reduced (1-->3)-alpha-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)-alpha-glucan, and then continues its hydrolysis towards the non-reducing end by releasing beta-glucose residues in a processive manner.

Citation

Christian H Grün, Nick Dekker, Alexander A Nieuwland, Frans M Klis, Johannis P Kamerling, Johannes F G Vliegenthart, Frans Hochstenbach. Mechanism of action of the endo-(1-->3)-alpha-glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum. FEBS letters. 2006 Jul 10;580(16):3780-6