Physicochemical properties of a novel alpha-L-arabinofuranosidase from Rhizomucor pusillus HHT-1

The zygomycete fungus Rhizomucor pusillus HHT-1, cultured on L(+)arabinose as a sole carbon source, produced extracellular alpha -L-arabinofuranosidas e. The enzyme was purified by (NH4)(2)SO4 fractionation, gel filtration, an d ion exchange chromatography. The molecular mass of this monomeric enzyme was 88 kDa. The native enzyme had a pI of 4.2 and displayed a pH optimum an d stability of 4.0 and 7.0-10.0, respectively. The temperature optimum was 65 degreesC, and it was stable up to 70 degreesC. The K-m and V-max for p-n itrophenyl alpha -L-arabinofuranoside were 0.59 mM and 387 mu mol.min(-1).m g(-1) protein, respectively. Activity was not stimulated by metal cofactors . The N-terminal amino acid sequence did not show any similarity to other a rabinofuranosidases. Higher hydrolytic activity was recorded with p-nitroph enyl alpha -L-arabinofuranoside, arabinotriose, and sugar beet arabinan; lo wer hydrolytic activity was recorded with oat-spelt xylan and arabinogalact an, indicating specificity for the low molecular mass L(+)-arabinose contai ning oligosaccharides with furanoside configuration.