One hundred fifty strains of actinomycetes were isolated from soils on plate cultures containing beet arabinan as the sole carbon source. About one-third of the culture fluids were found to have arabinosidase activity. A wild-type strain, Streptomyces sp. No. 17-1, was selected as the best producer of arabinosidase. The highest enzymatic activity was obtained in the culture fluid when the initial pH was adjusted to 9.0. An a-L-arabinofuranosidase was highly purified from the culture filtrate of No. 17-1 by combining column chromatography on DEAE-cellulose, gel filtration on Sephadex G-100, and isoelectric focusing. The molecular weight of the purified enzyme was estimated to be about 92,000, and its isoelectric point was pH 4.4. The enzymatic activity was maximumat pH 6.0 and was completely inhibited by Hg2 +. The apparent Kmvalue of the enzyme for^-nitrophenyl-a-L-arabinofuranoside was determined to be 3.6 mM.

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