Characterization of Cloned Endoxylanase from Cellulomonas sp. NCIM 2353 Expressed in Escherichia coli

A 22-kDa xylanase encoded by a cloned gene (XCs16) of Cellulomonas was purified to homogeneity with an overall yield of 44%. It is a basic protein with a pI of 8.1 and has a Km and Vmax of 3 mg/ml and 1150 μmoles/mg/min, respectively, for oat spelt xylan at 55°C and pH 5.8. Homologous xylanase from Cellulomonas could be identified with antibodies raised against purified xylanase encoded by XCs16. The enzyme from Cellulomonas also exhibited identical temperature and pH optimum and had a molecular weight of 23 kDa. Modification of tryptophan residue of purified xylanase resulted in the loss of xylanase activity. This loss could be reversed by the addition of substrate, indicating the involvement of tryptophan residue in the catalytic site.