Urease apoenzyme

Hu, L. T., Foxall, P. A., Russell, R. and Mobley, H. L. 1992, Purification of recombinant Helicobacter pylori urease apoenzyme encoded by ureA and ureB. 

Immunoprecipitation of urease or blue native gel electrophoresis established that urease apoenzyme is associated with the membrane protein, Urel, raising the possibility that the NH3 released during urease activity is able to diffuse rapidly through the inner membrane into the periplasm, decreasing the possibility of excessive alkalinization of the cytoplasm. 

The most likely explanation for the increase in urease activity seen with acidification is that there is a urea transporter in the bacteria. The urease gene cluster contains seven genes. There is a promoter followed by genes encoding the structural subunits, UreA and UreB. There is then a second promoter and then genes encoding Urel, -E, -F, -G, and -H. The last four are genes required for the assembly of active urease from the UreA-B apoenzyme by insertion of nickel, an essential cofactor in urease activity. UreE and -G and UreF and -H form heterodimers, and then a complex with UreA-B and nickel insertion occurs. 

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