Ten strains of Proteus penneri isolated from geographically diverse laboratories were tested for urease activity. Cell lysates from urea-induced cells had a mean activity of 4.9 +/- 4.1 mumol of NH3 per min per mg of protein. On nondenaturing 6% polyacrylamide activity gels, the enzymes of P. penneri had very similar electrophoretic mobilities within species and within the Proteus genus but were distinct from the ureases of Providencia and Morganella species. On lower-percentage polyacrylamide, differences in mobilities of the ureases could be detected between the Proteus species. From representative strains, the P. penneri urease was found to be inducible by growth in urea and had an apparent molecular weight of 246,000 +/- 9,000, an isoelectric point of 5.1, and a Km for urea of 14 mM and was inhibitable by acetohydroxamic acid, hydroxyurea, and EDTA. In an in vitro model of struvite formation, a P. penneri strain produced abundant crystals on a glass rod submerged in synthetic urine in the absence but not presence of acetohydroxamic acid (500 micrograms/ml).
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