Purification and characterization of an α-L-arabinofuranosidase from Clostridium acetobutylicum ATCC 824

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Abstract
An α-L-arabinofuranosidase (EC 3.2.1.55) has been purified from the extracellular culture fluid of Clostridium acetobutylicum ATCC 824 and characterized. The enzyme was a single polypeptide with a molecular weight of 94 000, an isoelectric point of 8.15, and a pH optimum between pH 5.0 and 5.5. The Km and Vmax values for p-nitrophenyl-α-L-arabinofuranoside were 4.0 mM and 36.4 μmol∙min−1·mg protein−1, respectively. The enzyme had practically no activity against other p-nitrophenylglycosides with the exception of p-nitrophenyl-α-D-glucoside which it hydrolysed at 9% of the rate exhibited on p-nitrophenyl-α-L-arabinofuranoside. It degraded arabinan in an exo-manner, but exhibited no activity on carboxymethylcellulose, arabinogalactan, arabinoxylan, or oat spelt xylan. However, when it was incubated with the purified xylanase B, also obtained from C. acetobutylicum, it acted cooperatively to increase the rate of hydrolysis of oat spelt xylan. Arabinose was detected as one of the hydrolysis products.