CHARACTERIZATION OF A METALLOPROTEASE FROM PSYCHROPHILIC XANTHOMONAS-MALTOPHILIA

An extracellular protease from psychrophilic Xanthomonas maltophilia isolated from alpine environment was purified and characterized. In spite of a comparable growth at 10-degrees-C and 20-degrees-C, protease excretion occurred only at 10-degrees-C. The enzyme was a 21-kDa protein with an isoelectric point higher than 9.5. The optimum pH and temperature for azocaseinolytic activity were 8.0 and 50-degrees-C respectively. The enzyme was stable up to 40-degrees-C but became inactive after 10 min at 60-degrees-C. The energy of activation was comparable to that of enzymes from mesophilic sources. Sensitivity to EDTA indicates that X. maltophilia protease is a metalloprotease.