X-RAY-ABSORPTION SPECTROSCOPY STUDY OF NATIVE AND PHENYLPHOSPHORODIAMIDATE-INHIBITED BACILLUS-PASTEURII UREASE

X-ray absorption spectroscopy (XAS) has been applied to urease from Ba cillus pasteurii, a highly ureolytic soil bacterium, with the aim of e lucidating the structural details of the nickel-containing active site . The results indicate the presence of octahedrally coordinated Ni2+, in a sphere of six N/O donors at an average distance of 0.203 nm. An a verage of two histidine residues are bound to nickel. The experimental evidence suggests direct binding of the urease inhibitor phenylphosph orodiamidate to Ni2+. These spectroscopic results are in agreement wit h previous findings on both plant and microbial ureases, but differ in some respect from the results obtained by X-ray crystallography analy sis of Klebsiella aerogenes urease.