Nickel enzymes comparison

Medina, M., Hatchikian, E. C. and Cammack, R. (1996) Studies of light-induced nickel EPR signals in hydrogenase Comparison of enzymes with and without selenium. Biochim. Biophys. Acta, 1275, 227-36. 

Urease (urea amidohydrolase) is an enzyme first identified over a hundred years ago in bacterial extracts [22], The presence of urease is a virulence factor for some pathogenic bacteria [23,24], It is now known to occur also in plants, fungi, and invertebrates (see [24,25] for reviews). Urease from jack bean was the first enzyme to be crystallized, in 1926. Almost 50 years later its metal content was reexamined and it was found to contain two atoms of nickel per subunit [26]. Finally in 1995 the crystal structure of the enzyme from the enteric bacterium Klebsiella aerogenes was determined [27], Amino-acid sequence comparisons predict that the structures of the plant and bacterial enzymes are similar, although with different subunit arrangements. 

Biophysical studies of the urease metal centre in the presence and absence of inhibitors, in conjunction with kinetic data provide the model of the bi-Ni site shown in 1. Certain inhibitors are thought to bridge the two nickel atoms consistent with a bridged transition state during urea hydrolysis. The ligands for nickel are believed not to contain sulphur, however, an essential cysteine is proximal to the active site. Comparisons of diethylpyrocarbonate reactivity for apo- and halo-enzyme are consistent with His as a ligand to nickel (Lee et al., 1990). 

Volbeda A, Fontecilla-Camps JC (2005) Structure-function relationships of nickel-iron sites in hydrogenase and a comparison with the active sites of other nickel—iron enzymes. Coord. Chem. Rev. 249 1609-1619... 

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