Holocytochrome-c synthase

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holocytochrome-c synthase
Holocytochrome-c synthase monomer, Thermus thermophilus
EC no.
CAS no.75139-03-6
IntEnzIntEnz view
ExPASyNiceZyme view
MetaCycmetabolic pathway
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO
Cytochrome c/c1 heme lyase

In enzymology, a holocytochrome-c synthase (EC is an enzyme that catalyzes the chemical reaction

holocytochrome c apocytochrome c + heme

Hence, this enzyme has one substrate, holocytochrome c, and two products, apocytochrome c and heme.

This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is holocytochrome-c apocytochrome-c-lyase (heme-forming). Other names in common use include cytochrome c heme-lyase, holocytochrome c synthetase, and holocytochrome-c apocytochrome-c-lyase. This enzyme participates in porphyrin and chlorophyll metabolism.

Cytochrome c haem-lyase (CCHL) and cytochrome Cc1 haem-lyase (CC1HL) are mitochondrial enzymes that catalyse the covalent attachment of a haem group on two cysteine residues of cytochrome c and c1. These two enzymes are functionally and evolutionary related. There are two conserved regions, the first is located in the central section and the second in the C-terminal section. Both patterns contain conserved histidine, tryptophan and acidic residues which could be important for the interaction of the enzymes with the apoproteins and/or the haem group.[1]

The human enzyme, HCCS, processes both cytochromes c and c1.[2]


  1. ^ Zollner A, Rodel G, Haid A (August 1992). "Molecular cloning and characterization of the Saccharomyces cerevisiae CYT2 gene encoding cytochrome-c1-heme lyase". Eur. J. Biochem. 207 (3): 1093–100. doi:10.1111/j.1432-1033.1992.tb17146.x. PMID 1499554.
  2. ^ Bernard DG, Gabilly ST, Dujardin G, Merchant S, Hamel PP (December 2003). "Overlapping specificities of the mitochondrial cytochrome c and c1 heme lyases". The Journal of Biological Chemistry. 278 (50): 49732–42. doi:10.1074/jbc.M308881200. PMID 14514677.
This article incorporates text from the public domain Pfam and InterPro: IPR000511