DETECTION AND PRELIMINARY CHARACTERIZATION OF EXTRACELLULAR PROTEOLYTIC ACTIVITIES OF THE HALOALKALIPHILIC ARCHAEON NATRONOCOCCUS-OCCULTUS

Extracellular proteolytic activity was detected in the haloalkaliphili c archaeon Natronococcus occultus as the culture reached the stationar y growth phase. Proteolytic activity was precipitated with ethanol and subjected to a preliminary characterization. Optimal conditions for a ctivity were attained at 60 degrees C and 1-2 M NaCl or KCl. Gelatin z ymography in the presence of 4 M betaine revealed a complex pattern of active species with apparent molecular masses ranging from 50 to 120 kDa. Experiments performed with inhibitors of the various groups of pr oteases indicated that the extracellular proteolytic enzymes of N. occ ultus are of the serine type. Individual protein species showed some d ifferences in salt and thermal stability.