A cold-active extracellular metalloprotease from Curtobacterium luteum (MTCC 7529): enzyme production and characterization.

A novel psychro-tolerant bacterium, Curtobacterium luteum, secreting an extracellular protease was isolated from the soil of Gangotri glacier, Western Himalaya. Maximum enzyme production was achieved when the strain was grown in a pH-neutral medium containing skim milk at 15 degrees C over 120 h. The metal ions such as Zn(2+) and Cr(2+) enhanced enzyme production. The specific activity of purified enzyme was 8,090 units/mg after 34.1-fold purification. The 115 kDa enzyme was a metalloprotease (activity inhibited by EDTA and EGTA) and showed maximum activity at 20 degrees C and pH 7. The enzyme was active over a broad pH range and retained 84% of its original activity between pH 6 and 8. There was no loss in enzyme activity when exposed for 3 h at 4-20 degrees C. However, the enzyme lost 65% of activity at 30 degrees C, and was almost inactivated at 50 degrees C, but was resistant to repeated freezing and thawing. The enzyme activity was stimulated by manganese ions; however, it was inactivated by copper ions.