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Multi-Heme Cytochromes & Enzymes

  1. Inês A. C. Pereira,
  2. António V. Xavier

Published Online: 15 MAR 2006

DOI: 10.1002/0470862106.ia278

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Pereira, I. A. C. and Xavier, A. V. 2006. Multi-Heme Cytochromes & Enzymes. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. Instituto de Tecnologia Química e Biologica, Oeiras, Portugal

Publication History

  1. Published Online: 15 MAR 2006


Multiheme c cytochromes and enzymes are a diverse group of proteins having several hemes c covalently bound to the polypeptide chain that are either enzymes involved in redox chemistry or electron transfer proteins. Most known members of this group are associated with the respiratory chains of proteobacteria. These proteins are characterized by a low amino acid to heme ratio, bis-histidinyl coordination (with a few exceptions), and low redox potentials of the hemes. The hemes are usually tightly packed in close contact, allowing very fast electron transfer. Despite the absence of overall sequence identity between proteins, the hemes are found in quite conserved structural motifs, which tend to be organized in diheme pairs that are either parallel or perpendicular to each other. From the structures available, two families can be recognized in terms of the heme structural arrangement: the cytochrome c3 family where the perpendicular motif is predominant, and the hydroxylamine oxidoreductase (HAO) family where the stacked parallel motif alternates with the perpendicular motifs. Other multiheme cytochromes for which the structure is not yet available may be part of novel structural families.


  • cytochromes;
  • hemes c;
  • multiheme;
  • electron transfer;
  • respiratory chain;
  • redox potential;
  • bacteria