Stereum purpureum endopolygalacturonase (EndoPG) IV was expressed in Aspergillus oryzae . Recombinant forms of EndoPG IV (rEndoPGs IV₀, IV₁, and IV₂) were purified from the culture filtrate by ammonium sulfate precipitation and two-step column chromatography with DE52 and hydroxyapatite. Each of these three recombinants was shown to be homogeneous by SDS-PAGE. Since it was predicted that the differences between them would be based on the number of sugar chains, the changes in molecular mass after enzymatic cleavage of the N -linked oligosaccharide with EndoH were determined by MALDI-TOF MS. From the data, the numbers of N -linked oligosaccharides were estimated to be 0, 1, and 2 for rEndoPG IV₀, IV₁, and IV_2, respectively. These sugar chains appeared to be a mixture of GlcNAc₂Hexose_5-10 and to include galactose as well as mannose. Mass analyses of IV_0, IV₁ and IV₂ after deglycosylation with EndoH demonstrated a hexose carbohydrate, suggesting the presence of an O -linked oligosaccharide that is lacking in native EndoPG IVs. The thermal denaturation curves of rEndoPG IV₀ and IV₁ based on CD analysis indicated T _m values of 60 and 59 °C, with a one-step thermal denaturation curve, similar to that of native EndoPG IV.