Crystalline Hydrolysis Research Articles

Mechanism of action of the endo-(1 → 3)-α-glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum

(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.

Synergistic actions of exo-type cellulases in the hydrolysis of cellulose with different crystallinities

The synergistic actions of pairs of seven different exo- and endo-type cellulases produced by Irpex lacteus (Ex-1 and En-1), Trichoderma reesei (CBH I, CBH II, and Endo-2), and Aspergillus niger (Exo-A and EG-1) were investigated using pure cellulosic materials with different crystallinities as substrates. A marked synergism was observed with certain combinations of exo-type cellulases, namely, CBH II and the other exo-type cellulases (Ex-1, CBH I, or Exo-A), when saccharification activity against crystalline and amorphous celluloses was investigated. Differences between the modes of action of each exo-type cellulase alone and in combination are not clearly observed; the production of cellobiose was accelerated during the hydrolysis of crystalline and amorphous celluloses by the combinations of exo-type cellulases, and no effective synergistic actions of the combinations of exo-type cellulases were noted in the depolymerization of crystalline cellulose. However, the synergistic actions of exo-type cellulases with CBH II caused specific changes in the surface features of highly crystalline celluloses. Characteristic morphological changes in cotton fibers (erosion and cracking of fiber surfaces) were induced at increasing rates by the combination of CBH II and Ex-1 or Exo-A. In contrast, destruction and subdivision of fibrils, which resulted in the pronounced fibrillation of cotton fibers, were observed after the treatment of cotton fibers with CBH II and CBH I. It was suggested that CBH II may be one of the key enzymes involved in the synergistic actions during cellulose hydrolysis.

Tryptic Hydrolysis of Crystalline and Non-crystalline Proteins from Phaseolus Beans

Tryptic Hydrolysis of Crystalline and Non-crystalline Proteins from Phaseolus Beans

Vibrational spectra of mercury(I) nitrate in aqueous solution and of the crystalline hydrolysis products

Aqueous solutions of 'mercurous nitrate' are shown by Raman spectra to contain the complexes [Hg2(OH2)NO3]+ and [Hg2(OH2)2]2+. Crystalline dimercury(I) nitrate, Hg2(NO3)2,2H2O, and its solid hydrolysis products Hg2(OH)2,3Hg2(NO3)2, 2Hg2(OH)2,3Hg2(NO3)2,H2O and Hg2(OH)2,- Hg2(NO3)2 have been obtained: the vibrational spectra are reported and interpreted in terms of possible structures. Modes v(Hg-Hg) appear in the range 170- 200 cm-1 and are sensitive to the particular combination of the ligands OH, ONO2, and H2O attached to the dimercury(I) ion.