Extracellular proteinases of pathogenic microorganisms
Moon, Jonathan Lloyd
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Proteolytic enzymes are required by all organisms for nutrient acquisition. However, pathogenic microorganisms often secrete enzymes of this class that may aid in their virulence by other means, including tissue destruction and modulation of host defense responses. It is therefore important to investigate the production of these enzymes by known pathogens. With this in mind, we have studied the production of proteolytic enzymes by two human pathogens, Penicillium marneffei and Staphylococcus epidermidis. P. marneffei is an AIDS related fungal pathogen, native to Southeast Asia. . Two proteinases secreted by Penicillium marneffei have been purified from liquid cultures. PMAP-1, a 24 kDa proteinase with optimal activity at acid pH, was purified from a culture grown at room temperature. PMNP, a 50 kDa serine protease with activity at neutral pH, was purified from a culture grown at 37°C. The cDNA for a third enzyme from P. marneffei, PMAP-2, was cloned. This putative proteinase has a predicted molecular weight of 22kDa and a pI of 4.41. Based on the amino terminal sequence and functionality of PMAP-1 and the full length sequence of the putative proteinase PMAP-2, both of these enzymes have been assigned to the G1 family of proteinases, also known as the eqolisins. S. epidermidis is a common nosocomial pathogen that is a frequent colonizer of indwelling medical devices. We have purified and characterized a proteinase secreted by this organism during culture at 37°C. This enzyme is a 25 kDa serine proteinase that has high homology to the V8 protease from Staphylococcus aureus and, like the latter enzyme, is highly specific for cleavage after glutamic acid residues. These three enzymes from P. marneffei and the one from S. epidermidis may play roles in virulence.