an extracellular xylanase was found to be the major protein in the filtrate culture of penicillium expansum when grown on 0.3 % wheat bran, which showed no xylanase multiplicity. the enzime was partial purified by.ammonium sulfate fractioning, molecular exclusion chromatography, ultrafiltration and anion exchange chromatography. the protein eluation profile showed only one form of xylanase that was partially characterized. the activity of purified xylanase was optimal at ph 5.5 and 40 oc. the enzyme was stable at ph between 5.5 and 6.5 and temperatures between 20-40 oc. the enzyme showed a km of 3.03 mm and vmax of 0.027 mmol min-1 mg -1 of protein. the enzymatic activity was increased 31 % by mg2+ and 28 % by al3+.