The catalytic center in nitrous oxide reductase, CuZ, is a copper-sulfide cluster.
Rasmussen T., Berks BC., Sanders-Loehr J., Dooley DM., Zumft WG., Thomson AJ.
The crystal structure of nitrous oxide reductase, the enzyme catalyzing the final step of bacterial denitrification in which nitrous oxide is reduced to dinitrogen, exhibits a novel catalytic site, called Cu(Z). This comprises a cluster of four copper ions bound by seven histidines and three other ligands modeled in the X-ray structure as OH(-) or H(2)O. However, elemental analyses and resonance Raman spectroscopy of isotopically labeled enzyme conclusively demonstrate that Cu(Z) has one acid-labile sulfur ligand. Thus, nitrous oxide reductase contains the first reported biological copper-sulfide cluster.