Open AccessKinetic properties of Helicobacter pylori urease compared with jack bean urease
Author(s) -
Cesareo Stephanie D.,
Langton Simon R.
Publication year - 1992
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1992.tb05535.x
Subject(s) - urease , canavalia ensiformis , chemistry , tris , phosphate , potassium phosphate , molecular mass , chromatography , buffer solution , helicobacter pylori , nuclear chemistry , sodium , enzyme , biochemistry , biology , organic chemistry , genetics
The urease proteins of the jack bean ( Canavalia ensiformis ) and Helicobacter pylori are similar in molecular mass when separated by non‐denaturing gradient polyacrylamide gel electrophoresis, both having three main forms. The molecular mass of their major protein form is within the range 440–480 kDa with the other two lesser forms at 230–260 kDa and 660–740 kDa. These forms are all urease active; however, significant kinetic differences exist between the H. pylori and jack bean ureases. Jack bean urease has a single pH optimum at 7.4, whereas H. pylori urease has two pH optima of 4.6 and 8.2 in barbitone and phosphate buffers that were capable of spanning the pH range 3 to 10. The H. pylori K m was 0.6 mM at pH 4.6 and 1.0 mM at pH 8.2 in barbitone buffer, greater than 10.0 mM, and 1.1 mM respectively in phosphate buffer and also greater than 10.0 mM in Tris · HCl at pH 8.2. By comparison, the jack bean urease had a K m of 1.3 mM in Tris · HCl under our experimental conditions. The findings show that the urease activity of H. pylori was inhibited at the pH optimum of 4.6 in the phosphate buffer, but not in the barbitone buffer. This was shown to be due to competitive inhibition by the sodium and potassium ions in the phosphate buffer, not the phosphate ions as suggested earlier. Jack bean urease activity was similarly inhibited by phosphate buffer but again due to the effect of sodium and potassium ions.