A new alkaline protease from Nocardiopsis sp., isolated from a soil sample collected from the Northeast of Brazil is reported. The crude extract (CE) was designate as partially purified extract (PPE) after purification with ammonium sulphate (0-20%). Optimal pH and temperature for detection of protease activity were obtaining at pH 10.5 and 8.0, for CE and PPE, respectively, at 50 degreesC for both extracts. The enzyme was stable at alkaline pH and more than 75% activity was retained even after incubation for 120 min at pH's between 8.0 and 10.5, for both extracts. The use of specific inhibitors, made it possible to show that the enzyme belongs to the group of serine protease. Maximum protease activity was achieved at pH 8.0 (50 U/mg) for CE and at pH 10.0 for PPE (1260 U/mg). The CE was partial purified with Sephadex G-75 obtained 26-purification fold and 34% yield. (C) 2002 Elsevier Science Ltd. All rights reserved.