Structural change of jack bean urease induced by addition surfactants studied with synchrotron‐radiation small‐angle X‐ray scattering

Both the quaternary and subunit structures of jack bean urease in solutions with ionic and nonionic surfactants have been studied by small‐angle X‐ray scattering using a synchrotron‐radiation source. The effects of those surfactants on the enzyme activity of urease have also been investigated in the same kind of solvent systems as those used for the scattering experiments. The present results show that the quaternary structure of urease in solution is fairly elongate and that by the relatively monor binding of SDS (SDS/protein = 0.23/1) the native urease molecule is dissociated into six identical subunits with nearly spherical structures. In addition the enzyme activity of urease was mostly retained under every solvent condition investigated, indicating that the subunit found in the present scattering experiments is the fundamental monomeric unit for both the quaternary‐structure formation and enzyme function of urease.