Heme-copper oxidase

Hammer-Nprskov d-band model, 70, 272-273, 327 Heme-copper oxidase, 610 High Throughput Synthesis of Nanoparticles, 572-574 Hydrogen (underpotential) adsorption, 60-63,254, 471-484, 526 Hydrogen evolution reaction (HER), 31, 79-87... 

Puustinen, A. and Wikstrom, M. (1999) Proton exit from the heme-copper oxidase of Escherichia coli. Proc. Natl. Acad. Sci. USA, 96, 35-7. 

Copper, Cu (d °), Cu " (d ) 3, trigonal planar A-Imidazole Electron transfer in Type III heme-copper oxidases (Cub in cytochrome c oxidase, for example)... 

Kopf, M.-A. Karlin, K. D. Models of copper enzymes and heme-copper oxidases, Biomimetic Oxidations Catalyzed by Transition Metal Complexes , Ed. Meunier, B. Imperial College Press London, 2000, pp. 309—362. 

The arrangement of the metal centers is in remarkable agreement with the structure, also reported in 1995 [49b], for another member of the superfamily of heme-copper oxidases, the cytochrome oxidase from Paracoccus denitrificans. The two structures show a strikingly similar coordination and arrangement of the five redox-active metals (the two irons and three coppers). 

HI. CONSTRUCTION OF THE CuB CENTER OF HEME-COPPER OXIDASES IN THE DISTAL SITE OF Mb... 

Kitagawa, Teizo and Ogura, Takashi, Oxygen Activation Mechanism at the Binuclear Site of Heme-Copper Oxidase Superfamily as Revealed by... 

Cytochrome bo ubiquinol oxidase from E. coli is a four-subunit heme-copper oxidase that catalyzes the four-electron reduction of O2 to water and functions as a proton pump (Puustinen et al., 1991 Fig. 11). All redox centers are located within the largest subunit (subunit I), with a low spin protoheme (heme b) acting as the electron donor to a binuclear center that is composed of an O-type heme (heme of) and a copper ion... 

Multicopper blue oxidases are synthesized as a single polypeptide chain, which is composed of three BCB domains in the case of laccases (LC) and ascorbate oxidases (AO) and six such domains in ceruloplasmin (CP) and hephaestin (HP). Structurally they are arranged in a triangular manner. These enzymes, along with heme-copper oxidases (cytochrome c oxidases and quinol-oxidases) and a cyanide-resistant alternative oxidase found in mitochondria of plants and fungi, are the only known enzymes capable of catalyzing four-electron reduction of dioxygen to water. In the... 

Kitagawa, T., and Ogura, T., 1997, Oxygen activation mechanism at the binuclear site of heme-copper oxidase superfamily as revealed by time-resolved resonance Raman spectroscopy, in Progress in Inorganic Chemistry, volume 45(K. D. Karlin ed.), John Wiley of Son, Inc, New Yorkpp. 4319479. 

In summary, the heme-copper oxidases provide two crucial functions in cell respiration O2 activation/reduction and energy conservation by redox-linked proton translocation. Significant progress has been made in this field since the first edition of this series in the understanding of both structure and function. X-ray structures at atomic resolution have now been solved for several heme-copper oxidases, " and this has provided an important basis for further functional work. A summary of the recent advances that have been made in understanding the architecture of the heme-copper oxidases and their metal-containing active sites and a discussion of insights into the molecular mehanisms of operation are presented here with special emphasis on important issues that still remain to be solved. 

Yoshikawa et al made the important statement that the role of heme a may be the biggest mystery in the stmcture and function of cytochrome c oxidase . It is indeed not at all obvious why all heme-copper oxidases have a low-spin heme group very close to the binuclear heme-copper site, especially since direct electron transfer from Cua to that site (if it occurred) would take place across almost the same distance. In the cytochrome c oxidases such direct electron transfer is effectively prevented, perhaps due to the bound Mg, the coordination sphere of which lies on the shortest path between... 

Nor is a member of the superfamily of heme-copper oxidases that also include the cytochrome oxidases (found e.g. in mitochondria ). Although no crystal structure of Nor is known at present, the number of transmembrane a-helices and the location and structure of their cofactors (heme c, heme b, heme bs and Fee) are highly similar to those of the cytochrome oxidases. 

Synthetic models for heme-copper oxidases 04CRV1077. 

The heme-copper oxidase superfamily is defined hy two criteria (1) a high degree of amino acid sequence similarity within the largest suhunit (suhunit I) and (2) a unique bimetallic active site, consisting of a heme and a closely associated copper atom (see Figure 8), where dioxygen is reduced to water. There are two main branches of the superfamily, which have distinct substrate specificities the mitochondrial respiratory oxidases use cytochrome r as a substrate and, hence, are called cytochrome c oxidases (COX). Bacteria, unlike most mitochondria, contain multiple respiratory oxidases. Many of the prokaryotic respiratory oxidases use membrane-bound quinol (ubiquinol or menaquinol) as a substrate rather than cytochrome c. A number of these quinol oxidases have been shown to be members of the heme-copper oxidase superfamily and to pump protons as efficiently as COXs. " ... 

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