A cold-active extracellular metalloprotease from Pedobacter cryoconitis--production and properties

An extracellular protease from Pedobacter cryoconitis, isolated from alpine cryoconite on glacier ice, was purified and characterized. Despite high cell densities at a temperature range of 1-25 degrees C, the optimum temperature for protease production was 15 degrees C. Maximum enzyme production was achieved when the strain was grown in a pH-neutral medium containing soybean meal, wheat flour and citrate over 72 h. The 27-kDa enzyme was a metalloprotease (sensitive to EDTA, EGTA and phenanthroline) and showed maximal activity towards azocasein at 40 degrees C and pH 8. The protease was stable for 60 min at 20-30 degrees C, lost 50% of activity after 30 min at 40 degrees C, and was inactivated at 50 degrees C, but was resistant to repeated freezing and thawing. Calcium ions had no protective effect against thermal denaturation. More than 80% of the maximum activity were retained at a pH in the range of 7-10. No activity loss was detected after 1 h at pH 7-9 and 20 degrees C, nor after 1 h of incubation with 3 M urea or 0.1% perborate.