An alkaline pectin lyase secreted by Aspergillus flavus MTCC 7589 was purified to electrophoretic homogeneity using ammonium sulphate fractionation, anion exchange chromatography on DEAE cellulose and gel filtration chromatography on sephadex G-100. The pH and temperature optima of the enzyme were found to be 8.0 and 50 degrees C. The enzyme was found to be stable for 24 h in the pH range 4.0-10.0. The enzyme does not loose activity up to 50 degrees C if exposed for 1 h. Addition of ammonium sulphate in the range of 0.1-2.0 M increased the thermostability of the enzyme, 0.6 and 1.8 M of ammonium sulphate providing complete stability at 60 and 70 degrees C respectively. The values of K-m and k(cat) of the enzyme were 0.59 mg/ml and 52.2 s(-1) respectively. The molecular weight was found to be 38 +/- 01 kDa. The purified enzyme showed efficacy in retting of Crotalaria juncea fibers. (C) 2008 Elsevier Ltd. All rights reserved.