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 p rotein with a pi of 8.1 and has a K-m and V-max of 3 mg/ml and 1150 mu moles/mg/min, respectively, for oat spelt xylan at 55 degrees C and p H 5.8. Homologous xylanase from Cellulomonas could be identified with antibodies raised against purified xylanase encoded by XCs16. The enzy me from Cellulomonas also exhibited identical temperature and pH optim um and had a molecular weight of 23 kDa. Modification of tryptophan re sidue of purified xylanase resulted in the loss of xylanase activity. This loss could be reversed by the addition of substrate, indicating t he involvement of tryptophan residue in the catalytic site.