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Appl. Environ. Microbiol., Jan 1995, 170-174, Vol 61, No. 1
S Gilead and Y Shoham
Bacillus stearothermophilus T-6 produced an alpha-L-arabinofuranosidase
when grown in the presence of L-arabinose, sugar beet arabinan, or oat
spelt xylan. At the end of a fermentation, about 40% of the activity was
extracellular, and enzyme activity in the cell-free supernatant could reach
25 U/ml. The enzymatic activity in the supernatant was concentrated against
polyethylene glycol 20000, and the enzyme was purified eightfold by
anion-exchange and hydrophobic interaction chromatographies. The molecular
weight of T-6 alpha-L- arabinofuranosidase was 256,000, and it consisted of
four identical subunits as determined by sodium dodecyl
sulfate-polyacrylamide gel electrophoresis and gel filtration. The native
enzyme had a pI of 6.5 and was most active at 70 degrees C and at pH 5.5 to
6.0. Its thermostability at pH 7.0 was characterized by half-lives of 53,
15, and 1 h at 60, 65, and 70 degrees C, respectively. Kinetic experiments
at 60 degrees C with p-nitrophenyl alpha-L-arabinofuranoside as a substrate
gave a Vmax, a Km, and an activation energy of 749 U/mg, 0.42 mM, and 16.6
kcal/mol, (ca. 69.5 kJ/mol), respectively. The enzyme had no apparent
requirement for cofactors, and its activity was strongly inhibited by 1 mM
Hg2+. T-6 alpha-L-arabinofuranosidase released L- arabinose from arabinan
and had low activity on oat spelt xylan. The enzyme acted cooperatively
with T-6 xylanase in hydrolyzing oat spelt xylan, and L-arabinose, xylose,
and xylobiose were detected as the end reaction products.(ABSTRACT
TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Purification and characterization of alpha-L-arabinofuranosidase from Bacillus stearothermophilus T-6
Department of Food Engineering and Biotechnology, Technion-Israel Institute of Technology, Haifa.
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