Unidirectional processive action of cellobiohydrolase Cel7A on Valonia cellulose microcrystals

• Published in: FEBS letters Vol. 432; no. 3; pp. 113 - 116
• Main Authors: Imai, Tomoya, Boisset, Claire, Samejima, Masahiro, Igarashi, Kiyohiko, Sugiyama, Junji
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 07.08.1998
• Subjects: Cellobiohydrolase Cel7A; Cellulase - metabolism; Cellulose - chemistry; Cellulose - metabolism; Cellulose - ultrastructure; Cellulose 1,4-beta-Cellobiosidase; Crystallization; Crystallography; Electron microdiffraction; Eukaryota - chemistry; Eukaryota - enzymology; Microscopy, Electron; Reducing end; Trichoderma viride; Valonia cellulose; Electron microdiffraction; Cellobiohydrolase Cel7A; Reducing end; Valonia cellulose; Trichoderma viride
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(98)00845-X

On the basis of the `parallel-up' structure of the cellulose crystal, a crystallographic approach to study the mode of action of cellobiohydrolase Cel7A on Valonia cellulose microcrystal has been carried out. After incubation with Cel7A, most of the initially smooth and well defined Valonia microcrystals displayed fibrillation. However, as the hydrolysis reaction was rather heterogeneous, some microcrystals remained superficially intact. Close investigation on such crystals revealed polar morphology: one end was narrowed extremely or pointed. Electron microdiffraction analysis of these crystals evidenced that the narrowing of the microcrystals occurs at their reducing end side. This was also confirmed by the visualization of selective reducing end labeling at the pointed ends of microcrystals. These lines of investigation are the first demonstration that the processivity of Cel7A action against insoluble highly crystalline celluloses is unambiguously toward non-reducing ends from reducing ends.