Biosynthesis, Structure, Function, and Regulation of Nitrous Oxide Reductase
Copper-containing enzymes are also involved in denitrification (the reduction of nitrate to nitrogen), which is a key component of the global nitrogen cycle. Extensive structural, spectroscopic, and chemical studies on nitrate reductase and nitrous oxide reductase are being pursued. These two classes of multicopper redox enzymes provide new opportunities to investigate structure/function relationships in copper-containing enzymes that are involved in denitrification. The principal goal of our research is to achieve a fundamental understanding of the structural and catalytic roles played by the metal ions and protein moieties in nitrate and nitrous oxide reductases. Questions concerning the possible regulation of these enzymes by intermediates in the denitrification pathway are also addressed. The intrinsic spectroscopic properties of Cu(II) are exploited as a built-in probe of the active site by variable temperature x-ray absorption (EXAFS), absorption, circular dichroism, magnetic circular dichroism, resonance Raman, and EPR spectroscopy. Some of the copper sites in the nitrite and nitrous oxide reductases are closely related to copper sites in other multicopper metalloenzymes. One of our principal findings is that nitrous oxide reductase contains CuA-type sites, which were first identified in cytochrome c oxidase. We have also identified a novel copper-sulfide cluster in the catalytic site of this enzyme. This is the first demonstration of a Cu4S cluster in chemistry and biochemistry. Integrating results from the proposed experiments and mechanistic studies will permit new structure/reactivity/function correlations among multi-copper oxidases and reductases to be formulated.
Chan, JM, Bollinger, JA, Grewell, CL, and Dooley, DM , "Reductively activated nitrous oxide reductase reacts directly with substrate ." JACS, 126, 3030-3031 (2004)
Alvarez, ML, Ai, J, Zumft, W, Sanders-Loehr, J, and Dooley, DM. , "Characterization of the copper-sulfur chromophores in nitrous oxide reductase by resonance raman spectroscopy: Evidence for sulfur coordination in the catalytic cluster. ." JACS, 123, 576-587, (2001)
Structure, Spectroscopy, Protein Chemistry, Mechanism, Inorganic, Bioinorganic