Purification and Characterization of an α-Mannosidase from the Tropical Fruit Babaco (Vasconcellea x Heilbornii Cv. Babaco)
2008
Blom, Hans | Reyes, Fernanda | Carlsson, Jan
An α-mannosidase (EC 3.2.1.24) present in the lyophilized latex of babaco (Vasconcellea heilbornii) has been purified to apparent homogeneity by native PAGE. The purification involves a three-step procedure with successive anion exchange with Q Sepharose HP, lectin affinity chromatography using ConA Sepharose 4B, and gel filtration using Superdex 200 prep grade. The molecular mass was determined to be in the range of 260-280 kDa by Superdex 200 prep grade gel filtration, and isoelectric focusing showed a pI range between 5.85 and 6.55, suggesting different glycosylated isoforms. The optimal temperature for the α-mannosidase was determined to lie between 50 and 60 °C, and the optimal pH was 4.5 at 50 °C. The K(m) value for p-nitrophenyl α-mannopyranoside (pNPM) was found to be 1.25 mM and the V(max), 2.4 μkat mg-1 at 50 °C and 1.94 μkat mg-1 at 40 °C. The pure α-mannosidase was specific for mannose and did not display activity for any other tested synthetic substrates.
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