[Associated synthesis of some secreted pathogenicity factors of Klebsiella pneumoniae].

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.

[Protease activity of Klebsiella pneumoniae of different virulence]. / Proteaznaia aktivnost' Klebsiella pneumoniae razlichnoi virulentnosti.

The study of substrate specificity and activity of proteolytic enzymes secreted by K. pneumoniae strains with different virulence was carried out. The strains were cultivated in a liquid semi-synthetic medium. The biomass was inactivated, and the supernatant fluid was separated from microbial cells by centrifuging. In the supernatant thus obtained and in the fractions isolated by gel filtration with the subsequent purification on DEAE Sepharose elastase-like, trypsin-like and chemotrypsin-like proteolytic activity was determined. In K. pneumoniae strains with different virulence only a single proteolytic enzyme--elastase with a mol. wt. of 21 kD--was detected. The protease activity of the supernatant culture fluid did not depend on the virulence of the strain and was equal to 5,416-7,476 I.U./ml. The activity of the purified enzyme was 100% of the elastase-like activity of the supernatant culture fluid. The most virulent K. pneumoniae strain K2, whose LD50 for white mice was less than 10 microbial cells, was characterized by lower elastase-like activity. The absence of correlation between protease activity and K. pneumoniae virulence may be explained by the fact that surface glycoproteins of eukaryotic cells are glycosilated and thus slightly accessible for proteases.