AbstractAn endo‐β‐1,4‐glucanase (EC 3.2.1.4) was obtained in high yields in purified form a culture filtrate ofFusarium liniby an extremely simple method. The method consists of precipitation of the culture filtrate with ammonium sulphate (290 g/L), followed by chromatography of the precipitated fraction on Biogel P‐150. The purification is based on the unusual property of the enzyme being eluted after cytochrome C, even though it molecular weight is 2.8 × 104(by SDS PAGE). The yield of pure enzyme was 6.8 mg/L culture broth. The homogeneity of the enzyme was established by ultracentrifugation, isoelectric focusing, and electrophoresis in polyacrylamide gels containing SDS. The enzyme was isoelectric at pH 8.3 and contained 2.9% carbohydrate. TheKmvalue for carboxymethyl (CM) cellulose was 11.6 mg/mL. The enzyme showed high viscosity reducing activity towards CM cellulose but very low activity with Walseth cellulose and crystalline celluloses such as Avicel and cotton. The purified enzyme has activity towards xylan. The amino acid analysis showed a predominance of acidic and neutral amino acids and low contents of histidine, arginine, and methionine. One‐half of the cysteine content was 11 residues/mol enzyme, and no free–SH group w