Imai T, Boisset C, Samejima M, Igarashi K, Sugiyama J
Wood Research Institute, Kyoto University, Uji, Japan.
FEBS Lett. 1998 Aug 7;432(3):113-6. 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.
基于纤维素晶体的“平行向上”结构，开展了一项晶体学研究，以探究纤维二糖水解酶Cel7A对瓦洛尼亚纤维素微晶的作用模式。用Cel7A孵育后，大多数最初光滑且轮廓清晰的瓦洛尼亚微晶出现了原纤化。然而，由于水解反应相当不均匀，一些微晶表面仍保持完整。对这些晶体的仔细研究揭示了极性形态：一端极度变窄或呈尖状。对这些晶体的电子微衍射分析表明，微晶的变窄发生在其还原端一侧。微晶尖端部的选择性还原端标记可视化也证实了这一点。这些研究首次证明，Cel7A对不溶性高度结晶纤维素的作用持续性明确地是从还原端朝向非还原端。
