The tetranuclear copper active site of nitrous oxide reductase: the CuZ center

Abstract

This review focuses on the novel CuZ center of nitrous oxide reductase, an important enzyme owing to the environmental significance of the reaction it catalyzes, reduction of nitrous oxide, and the unusual nature of its catalytic center, named CuZ. The structure of the CuZ center, the unique tetranuclear copper center found in this enzyme, opened a novel area of research in metallobiochemistry. In the last decade, there has been progress in defining the structure of the CuZ center, characterizing the mechanism of nitrous oxide reduction, and identifying intermediates of this reaction. In addition, the determination of the structure of the CuZ center allowed a structural interpretation of the spectroscopic data, which was supported by theoretical calculations. The current knowledge of the structure, function, and spectroscopic characterization of the CuZ center is described here. We would like to stress that although many questions have been answered, the CuZ center remains a scientific challenge, with many hypotheses still being formed.

The electron transfer complex between nitrous oxide reductase and its electron donors

“…[54]. The electron transfer pathway identified above is in agreement with this mechanism, in which the reduction of the CuZ center occurs prior to substrate binding.…”

Biochemical characterization of the purple form of Marinobacter hydrocarbonoclasticus nitrous oxide reductase

“…Although the spectroscopic, electronic and structural properties of the CuZ centre in the resting state have been extensively characterized [14], this state is redox inactive in the sense that it cannot be oxidized or easily reduced, and it is also catalytically inactive, as its specific activity is very low when compared with that of the enzyme with the CuZ centre in the fully reduced state [18,19].…”

“…It has been hypothesized that this long activation process corresponds to a rearrangement in the coordination sphere of the CuZ centre, which is required for full activity [14].…”

“…Therefore, it seems that a Also named as a purple form by some authors. b In the 'blue form' of N 2 OR, the CuZ centre is found mainly in the CuZ* state, which has also been named 'resting CuZ' [14]. The two dithionite-reduced forms of N 2 OR are different, although both copper centres have the same redox state.…”

Direct electron transfer from pseudoazurin to nitrous oxide reductase in catalytic N2O reduction

“…We believe the new crystallographic data and the results reported herein are entirely consistent. Although substantial experimental evidence has been presented that the fully reduced [4Cu(I)] form of Cu Z is the catalytically competent state of N 2 OR [17][18][19][20] others have presented plausible arguments for other Cuz states to fulfill this role [21] .…”