An inducible extracellular exoinulinase (isoform II) was purified from the extracellular extract of Aspergillus fumigatus by ammonium sulphate precipitation, followed by successive chromatographies oil DEAE-Sephacel, Octyl-Sepharose (HIC) Sephacryl S-200, affinity chromatography on ConA-CL Agarose and Sephacryl S-100 columns. The enzyme was purified 75-folds with 3.2%, activity yield from the starting culture broth. The purified isoform II was a monomeric 62 kDa protein with a pI value of 4.5. The enzyme showed maximum activity at pH 6.0 and was stable over a pH range of 4.0-7.0, whereas the optimum temperature for enzyme activity was 60 degrees C. The inulinase isoform II showed exo-inulinolytic activity and retained 72% and 44% residual activity after 12 h at 60 degrees C and 70 degrees C, respectively. The inulin hydrolysis activity was completely abolished with 5 mM Hg2+ and Fe2+, whereas K+ and Cu2+ enhanced the inulinase activity. As compared to sucrose, stachyose and raffinose the purified enzyme had a lower K-m(1.25 mM) and higher catalytic center activity (K-cat = 3.47 x 10(4) min(-1)) for inulin. As compared to exoinulinase isoform 1 of A. fumigatus, purified earlier, the isoform II is more thermostable and is a potential candidate for commercial production of fructose from inulin. (c) 2005 Elsevier Ltd. All rights reserved.