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pubmed:abstractText |
The study was carried out to evaluate the substrate specificity and activity of proteases secreted by strains of Klebsiella pneumoniae with various degree of virulence. The process included cultivation of the strains in semi-synthetic medium, after which the biomass was inactivated and the supernatant was separated from bacterial cells through centrifugation. Elastase-, trypsin-, and chymotrypsin-like proteolytic activity was measured in the supernatant and in all fractions obtained through gel-filtration, followed by DEAE-sepharose purification. Regardless of the degree of virulence, all the studied strains of K. pneumoniae secreted only one proteolitic enzyme, which was elastase with molecular weight of about 21 kDa. Addition of glycoprotein--the main structural component of eucaryotic cells--into the culture medium in the beginning of incubation, increased protein, polysaccharide, and lipopolysaccharide synthesis; proteolythic activity in the supernatant fluid increased from 7,476 to 15,731 mU/ml. The increase was associated with an elevation of polysaccharide synthesis from 173 to 349 mg dry weight. However, proteolythic activity per 1 gr of polysaccharide did not increase; it was 43.3 and 45.1 units, respectively. Thus, proteolytic activity increased in direct propotion to the increase of polysaccharide synthesis into the culture medium.
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