RESUMO
Thermostable alkaline metalloprotease (EC 3.4.24.4), a simple protein of very low molecular mass (11 kDa), was isolated and purified from the cell free broth of Streptomyces diastaticus sp SS1 by concentration, (NH4)2SO4 precipitation and affinity chromatography over casein. The isoelectric point of the protease is 7.2. The temperature and pH optima for the enzyme activity are 37 degrees C and 8 respectively. The half life of the enzyme at 55 degrees C is 24 hr and the enzyme is stable over a pH range of 7.5 to 9. The K(m) value of the enzyme was estimated to be 2 x 10(-3) mg ml-1. Ca2+ is essential for enzyme activity as well as thermal stability. The alpha-helix content of the metalloprotease is calculated to be 50% from the circular dichroism spectrum. The number of Zn2+ binding to each molecule of protease is determined to be one by atomic absorption.