Abstract
Background: The extracellular β-glucosidases (cellulose and xylan induced) and xylan-induced β-xylosidase from Aspergillus niger NCIM 1207 were purified to homogeneity. The protocols were based on fractional ethanol precipitation, pH and thermal stability, and separation of impurities by thermal denaturation. Results: The molecular weights of all the three enzymes were 122 and 336 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel perme\ation chromatography. Mass spectrometric analysis revealed that cellulose and xylan-induced β-glucosidases showed 24 and 12% sequence coverage, respectively, with β-glucosidase A of A. niger CBS 513.88/FGSC A1513. Xylan-induced β-xylosidase exhibited 35% homology with probable exo-1,4-β-xylosidase of A. niger CBS 513.88/FGSC A1513 and 11% homology with β-glucosidase A of A. niger CBS 513.88/FGSC A1513. Conclusion: The enzymes are high-molecular weight proteins and are trimeric in nature. This is the first report on high-molecular weight trimeric β-xylosidase from fungal species.
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