Cytochrome c Oxidase

Abstract

Cytochrome c oxidase is the key enzyme of cell respiration in all eukaryotes and many prokaryotes. The cytochrome c oxidases belong to the haem–copper superfamily of structurally and functionally related enzymes; though related in structure, some bacterial variants lack amino acid residues that are known to be obligatory for the function of the members of the main family. All haem–copper oxidases have a unique bimetallic active site catalysing reduction of dioxygen (O 2 ) to water and an adjacent second haem group that donates electrons to this site. Here, the mechanism of O 2 reduction is reviewed. The membrane‐bound enzyme couples this reaction to translocation of protons across the membrane, and thus functions as a primary energy transducer that contributes to the formation of ATP (adenosine triphosphate) in aerobic life. The most recent knowledge of the function of this ‘proton pump’ is discussed. It is concluded that cytochrome c oxidase is an electrostatic energy‐transducing machine with high efficiency. Key Concepts: Cytochrome c oxidase is an electrostatically coupled energy transducer. The high affinity for O 2 is due to kinetic ligand trapping. O 2 reduction in cell respiration yields no reactive oxygen species.

Efficient Zero-Knowledge Argument for Correctness of a Shuffle

“…We compare this implementation on the parameter setting for ElGamal encryption used in [8] and find significant improvements in both communication and computation. We also compare our implementation to the shuffle argument in the Verificatum mix-net [29] and find significant improvements in communication and moderate improvements in computation.…”

“…Furthermore, Terelius and Wikström [25] constructed conceptually simple shuffle arguments that allowed the restriction of the shuffles to certain classes of permutations. Both protocols are implemented in the Verificatum mix-net library [29].…”

“…First, we compare the theoretical performance of the schemes without any optimization. Second, we compare an implementation of our protocol with the implementation by Furukawa et al [8] and with the implementation in the Verificatum mix-net library [29].…”

“…Recently Wikström made a complete implementation of a mix-net in Java in [29] called Verificatum, which is based on the shuffle argument in [25]. To produce comparable data, we ran the demo file with only one mix party in the non-interactive mode Table 4.…”

“…Acknowledgment. We would like to thank Douglas Wikström for discussions and help regarding our comparison with the shuffle argument used in Verificatum [29].…”