The enzyme cysteine lyase (EC 4.4.1.10)
catalyzes
Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
the
chemical reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...
:
L-cysteine + sulfite
L-cysteate +
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
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
Redox ( , , reduction–oxidation or oxidatio ...
s, specifically the class of carbon-sulfur lyases. The
systematic name
A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature.
A semisystematic name or semitrivi ...
of this enzyme class is
L-cysteine hydrogen-sulfide-lyase (adding sulfite;
L-cysteate-forming). Other names in common use include cysteine (sulfite) lyase, and
L-cysteine hydrogen-sulfide-lyase (adding sulfite). This enzyme participates in
cysteine
Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...
and
taurine metabolism. It employs one
cofactor,
pyridoxal phosphate
Pyridoxal phosphate (PLP, pyridoxal 5'-phosphate, P5P), the active form of vitamin B6, is a coenzyme in a variety of enzymatic reactions. The International Union of Biochemistry and Molecular Biology has catalogued more than 140 PLP-dependen ...
.
Evolution
Genes encoding cysteine lyase (CL) originated around 300 million years ago by a tandem
gene duplication
Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene ...
and
neofunctionalization
Neofunctionalization, one of the possible outcomes of functional divergence, occurs when one gene copy, or paralog, takes on a totally new function after a gene duplication event. Neofunctionalization is an adaptive mutation process; meaning one ...
of
cystathionine β-lyase (CBS) shortly after the split of mammalian and reptilian lineages. CL genes are found only in ''
Sauropsida
Sauropsida (Greek language, Greek for "lizard faces") is a clade of amniotes, broadly equivalent to the Class (biology), class Reptile, Reptilia, though typically used in a broader sense to also include extinct stem-group relatives of modern repti ...
'' where they are involved in a metabolic pathway for
sulfur metabolism
Sulfur is metabolized by all organisms, from bacteria and archaea to plants and animals. Sulfur can have an oxidation state from −2 to +6 and is reduced or oxidized by a diverse range of organisms. The element is present in proteins, sulfate est ...
in the chicken egg.
References
EC 4.4.1
Pyridoxal phosphate enzymes
Enzymes of unknown structure
{{lyase-stub