Alpha-L-rhamnosidase from Aspergillus clavato-nanicus MTCC-9611 active at alkaline pH

An alpha-L-rhamnosidase secreting fungal strain has been isolated and identified as Aspergillus clavato-nanicus MTCC-9611. The enzyme was purified to homogeneity from the culture filtrate of the fungus using concentration by ultrafiltration membrane and ion-exchange chromatography on CM-cellulose. The native PAGE analysis confirmed the homogeneity of the purified enzyme. The SDS-PAGE analysis of the purified enzyme revealed a single protein band corresponding to the molecular weight 82 kDa. The alpha-L-rhamnosidase activity of Aspergillus clavato-nanicus MTCC-9611 had optimum at pH 10.0 and 50 degrees C. The K(m) values of the enzyme were 0.65 mM and 0.95 mM using p-nitrophenyl alpha-L-rhamnopyranoside and naringin as a substrates respectively. The enzyme transforms naringin to prunin at pH 10.0 and further hydrolysis of prunin to naringenin does not occur under these reaction conditions that makes alpha-L-rhamnosidase activity of Aspergillus clavatonanicus MTCC-9611 promising enzyme to get prunin for pharmaceutical purposes.