Expression and partial characterization of an elastase from Chromobacterium violaceum

Chromobacterium violaceum was recovered at necropsy from the lungs, liver, spleen, and an interscapular abscess of a Chinese red panda (strain 98-9187) [J. Vet. Diagn. Invest. 12 (2000) 177]. As the lungs exhibited extensive, necrotizing lesions harboring bacterial aggregates, we sought to determine whether C. violaceum produced an elastase that might in part account for these lesions. The C. violaceum type strain (ATCC 12472 T) and strain 98-9187 were shown to exhibit elastolytic activity by elastin Congo red and elastin nutrient agar assays. The activity was isolated from the periplasmic fraction and was present throughout the growth cycle. Activity increased markedly in late logarithmic phase growth. In elastin-limiting medium, activity rapidly decreased in early stationary phase indicating a tight regulation of yield. The activity was optimal at neutral pH and was sensitive to the metalloproteinase inhibitors EDTA and 1,10-phenanthroline. Activity was restored upon addition of zinc indicating the enzyme is a zinc metalloproteinase. A band corresponding to purified elastase activity was present at ∼30 kDa in a denaturing polyacrylamide gel.