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The present study demonstrates that Sporisorium reilianum , a phytopathogenic fungus of corn, produces intracellular xylanolytic activity during submerged fermentation. Production reached its highest levels in a medium containing glucose, corn hemicellulose and yeast extract. An intracellular xylanase was purified by a process that included precipitation with ammonium sulfate, ion exchange chromatography and gel filtration. Optimal pH and temperature values were 5.0 and 60 °C, respectively. The enzyme showed activity through a broad pH range. The molecular weights of pure xylanase were 36 and 37 kDa, determined by SDS PAGE and gel filtration, respectively. K m and V max were 0.160 mg/mL and 1.564 μmol/min/mg, respectively, on a substrate of birchwood xylan. SDS, EDTA, β-Mercaptoethanol, Tween 80, Triton and Mn2+ and Ca2+ strongly inhibited activity. The purified enzyme hydrolyzed xylan, releasing xylotriose and xylobiose. Sequence protein analysis showed 95% similarity with the theoretical protein encoded by the sr14403 gene of S. reilianum , which encodes a putative endo-β-1,4-xylanase. The enzyme is an isoform of the extracellular xylanase SRXL1 of this basidiomycete. • Sporisorium reilianum showed intracellular xylanolytic activity. • An intracellular xylanase from S. reilianum was purified with a molecular weight of 37 kDa. • The xylanase intracellular is an isoform of the xylanase extracellular SRXL1. • Using birch xylan as substrate the Km = 0.160 mg/mL and Vmax = 1.564 μmol/mL/min. • The enzyme hydrolyzed the xylan, releasing xylotetrose, xylotriose and xylobiose. [ABSTRACT FROM AUTHOR]