Degradation of soluble laminin and depletion of tissue-associated basement membrane laminin by Pseudomonas aeruginosa elastase and alkaline protease.

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Purified Pseudomonas aeruginosa elastase and alkaline protease rapidly cleaved soluble laminin, with each enzyme yielding different cleavage products. These cleavage fragments were separated from the intact laminin A and B polypeptide chains by sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis and detected by their characteristic Coomassie blue staining patterns. Pseudomonas elastase produced rapid and extensive degradation of both A and B chains, including the disulfide-rich regions. Apparently complete degradation to limit digests was obtained after 30 min with a substrate/enzyme ratio of 30:0.5. Under similar conditions, alkaline protease rapidly degraded the A chain while slowly degrading the B chain. In addition, immunoreactive laminin was released from authentic basement membranes after incubation with either enzyme as detected by an enzyme-linked immunoabsorption assay and by immunofluorescence. The results from these studies suggest a direct role for elastase and alkaline protease in both tissue invasion and hemorrhagic tissue necrosis in P. aeruginosa infections.

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