Crystallization and preliminary X-ray characterization of a thermostable low-molecularweight 1,4-$\beta$-D-glucan glucohydrolase from an alkalothermophilic Thermomonospora sp.

Cellulases catalyze the hydrolysis of $\beta-1,4$glycosidic linkages within cellulose, the most abundant organic polymer on earth. The cellulase (TSC; EC 3.2.1.4) from an alkalothermophilic Thermomonospora sp. has a low molecular weight of 14.2 kDa. It is optimally active at 323 K and stable over the wide pH range of 5-9. Moreover, it has bifunctional activity against cellulose and xylan polymers. In this study, TSC was purified from the native source and crystallized by the hanging-drop vapour-diffusion method. The crystals belong to the orthorhombic space group $P2_12_12_1$, with unit-cell parameters a = 49.9, b = 79.5, c = 99.7 $\AA$, and diffract to better than 2.3 $\AA$ resolution