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  • Title: Mechanism of action of the endo-(1-->3)-alpha-glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum.
    Author: Grün CH, Dekker N, Nieuwland AA, Klis FM, Kamerling JP, Vliegenthart JF, Hochstenbach F.
    Journal: FEBS Lett; 2006 Jul 10; 580(16):3780-6. PubMed ID: 16780840.
    Abstract:
    (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.
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