X-ray absorption spectroscopy study of native and phenylphosphorodiamidate-inhibited Bacillus pasteurii urease

X-ray absorption spectroscopy (XAS) has been applied to urease from Bacillus pasteurii, a highly ureolytic soil bacterium, with the aim of elucidating 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 average of two histidine residues are bound to nickel. The experimental evidence suggests direct binding of the urease inhibitor phenylphosphorodiamidate to Ni2+. These spectroscopic results are in agreement with previous findings on both plant and microbial ureases, but differ in some respect from the results obtained by X-ray crystallography analysis of Klebsiella aerogenes urease.