A thermostable α-arabinofuranosidase from xylanolytic Bacillus pumilus:: purification and characterisation

Bacillus pumilus PS213 secretes an alpha-L-arabinofuranosidase (AF) when grown in the presence of arabinogalactan or oat meal. The enzyme has been purified to homogeneity and characterised. Its molecular mass, as determined by gel filtration, is 220 kDa, while sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed a single band of approximately 60 kDa. According to the result of the mass spectrometry analysis showing a molecular mass of 56 kDa, the enzyme should be a homotetramer. The isoelectric point was found to be 5.2, the enzyme activity was optimal at 55 degreesC and pH 7.0. The enzyme retained 80% of its activity after 2 h at 65 degreesC and lost 50% of activity at 75 degreesC after 135 min. The Michaelis constant K-m and V (max) for p-nitrophenylarabinofuranoside at 37 degreesC were 1.7 mM and 52.9 U mg(-1), respectively. N-terminal sequence analysis and internal peptide fragments showed homology with glycosyl hydrolases of family 51. (C) 2002 Elsevier Science B.V. All rights reserved.