Properties of urease from Ureaplasma urealyticum: kinetics, molecular weight, and demonstration of multiple enzyme isoelectric point forms.

In the several strains of Ureaplasma urealyticum that we examined, all originally isolated from human sources, the ureases were found to have a pH optimum between 7.2 and 7.5, and the Km was approximately 2.5 mM urea. Using nonreducing, nondenaturing conditions for polyacrylamide gel electrophoresis, the molecular weight of the holoenzyme was determined to be approximately 380 000. Treatment with reducing agents did not affect the electrophoretic mobility and, therefore, the molecular weight of ureaplasma urease. Immunoblot analysis (using antiserum to U. urealyticum urease) after sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing, denaturing conditions revealed two antigenically reactive bands of molecular weight 174 000 and 179 000. Under reducing, denaturing conditions, a single band of molecular weight approximately 179 000 was detected. Multiple forms of urease were detected by isoelectrofocusing but not by zonal electrophoresis.