alpha-Mannosidase is a key enzyme in processing and degradation of N-glycans in plants and animals. In the present study alpha-mannosidase from crude extracts of Dolichos lablab (Indian beans) has been purified by ammonium sulfate precipitation, anion exchange, galactose Sepharose, phenyl Sepharose, gel permeation and Con A Sepharose chromatography. The purified protein migrated as a single band corresponding to 116 kDa on SDS-PAGE under reducing conditions. The pH and temperature optima of alpha-mannosidase activity determined by use of p-nitrophenyl-alpha-D-mannopyranoside as substrate were found to be 5.0 and 60-65 degrees C, respectively. The K-M was 1.48 mM and swainsonine was a potent inhibitor of the enzyme with IC50 value 50-80 nM. Additionally, the de novo amino acid sequencing showed active site regions highly conserved among other plant acidic alpha-mannosidases and yielded sequence coverage of approximately 32.5%. N-glycopeptide analysis revealed the presence of paucimannosidic type structure in a conserved N-glycosylation site as well as at least one oligo mannosidic glycan at an undetermined site after ZIC-HILIC enrichment of proteolytic glycopeptides. The partial biochemical and molecular characterization of this enzyme reveals that it is a class II alpha-mannosidase from the glycosyl hydrolase family 38. (C) 2013 Elsevier Inc. All rights reserved.