Bifidobacterium adolescentis Int-57 isolated from human faeces produced extracellular amylase. The enzyme was purified from the culture supernatant fluids by ammonium sulphate precipitation, gel-filtration chromatography (Sephadex-G-75), ion-exchange chromatography (CM-cellulose) and FPLC. SDS-PAGE of the purified enzyme revealed a major band with an apparent molecular weight of 66 kDa. The pI was 5.2. Enzyme activity was optimal at 50 degrees C, and at pH 5.5. The enzyme was stable at 20-40 degrees C, and at pH 5-6 with a K(m) value of 2.4 g l-1 soluble starch. The activation energy was 42.3 kJ mol-1. The enzyme was significantly inhibited by maltose (10%), glucose (10%), Cu2+ (5 mmol l-1), Zn2+ (5 mmol l-1), N-bromosuccinimide (5 mmol l-1), EDTA (5 mmol l-1), I2 (1 mmol l-1) and activated by beta-mercaptoethanol (10 mmol l-1).