I have never worked on Urease but If one subunit equals 90.7 kDa and and a non-covalent homo-hexamer is 544.620 kDa, then running a 10% SDS-PAGE gel should allow you to visualise the protein of interest.
So if you have never performed an SDS-PAGE gel before then try this protocol -
If you are running the usual SDS-PAGE under reducing conditions, you should only find one band at 90kDa. If you divide the urease molecular weight by the mol. weight of the subunit, it is clear that it is composed of 6 units. 90kDa is in the molecular weight range of the usually used gels used for SDS-PAGE, and no special gels are therefore required.
Your sample buffer should contain all the reagents to denature urease: SDS, reducing agent (mercaptoethanol, DTT, etc.). Then you just have to heat the sample/