A xylanase-encoding gene, xyn11F63, was isolated from Penicillium sp. F63 CGMCC1669 using degenerated polymerase chain reaction (PCR) and thermal asymmetric interlaced (TAIL)-PCR techniques. The full-length chromosomal gene consists of 724 bp, including a 73-bp intron, and encodes a 217 amino acid polypeptide. The deduced amino acid sequence of xyn11F63 shows the highest identity of 70% to the xylanase from Penicillium sp. strain 40, which belongs to glycosyl hydrolases family 11. The gene was overexpressed in Pichia pastoris, and its activity in the culture medium reached 516 U ml(-1). After purification to electrophoretic homogeneity, the enzyme showed maximal activity at pH 4.5 and 40A degrees C, was stable at acidic buffers of pH 4.5-9.0, and was resistant to proteases (proteinase K, trypsin, subtilisin A, and alpha-chymotrypsin). The specific activity, K (m), and V (max) for oat spelt xylan substrate was 7,988 U mg(-1), 22.2 mg ml(-1), and 15,105.7 mu mol min(-1) mg(-1), respectively. These properties make XYN11F63 a potential economical candidate for use in feed and food industrial applications.