The enzyme holocytochrome-''c'' synthase (EC 4.4.1.17)
catalyzes
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
the
chemical reaction
:holocytochrome ''c''
apocytochrome ''c'' + heme
This enzyme belongs to the family of
lyase
In biochemistry, a lyase is an enzyme that catalyzes the breaking (an elimination reaction) of various chemical bonds by means other than hydrolysis (a substitution reaction) and oxidation, often forming a new double bond or a new ring structure. ...
s, 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
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
metabolism.
Cytochrome ''c'' heme-lyase (CCHL) and cytochrome Cc1 heme-lyase (CC1HL) are
mitochondrial
A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is use ...
enzymes that catalyze the
covalent attachment of a heme group on two
cysteine
Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile.
When present as a deprotonated catalytic residue, sometime ...
residues of
cytochrome c
The cytochrome complex, or cyt ''c'', is a small hemeprotein found loosely associated with the inner membrane of the mitochondrion. It belongs to the cytochrome c family of proteins and plays a major role in cell apoptosis. Cytochrome c is hig ...
and c1. These two
enzymes
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
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 heme group.
The human enzyme,
HCCS, processes both cytochromes ''c'' and ''c1''.
References
*
EC 4.4.1
Enzymes of unknown structure
{{enzyme-stub