Cystathionine

Cystathionine is an intermediate in the synthesis of cysteine from homocysteine. It is produced by the transsulfuration pathway and is converted into cysteine by cystathionine gamma-lyase (CTH).

Cystathionine

Names
IUPAC name S-((R)-2-amino-2-carboxyethyl)-L-homocysteine
Other names L-Cystathionine; S-[(2R)-2-Amino-2-carboxyethyl]-L-homocysteine
Identifiers
CAS Number	56-88-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:17755 Y
ChEMBL	ChEMBL209241 Y
ChemSpider	388392 N
ECHA InfoCard	100.000.269
KEGG	C00542 Y
MeSH	Cystathionine
PubChem CID	439258
UNII	375YFJ481O Y
CompTox Dashboard (EPA)	DTXSID20971384
InChI InChI=1S/C7H14N2O4S/c8-4(6(10)11)1-2-14-3-5(9)7(12)13/h4-5H,1-3,8-9H2,(H,10,11)(H,12,13)/t4-,5-/m0/s1 N Key: ILRYLPWNYFXEMH-WHFBIAKZSA-N N InChI=1/C7H14N2O4S/c8-4(6(10)11)1-2-14-3-5(9)7(12)13/h4-5H,1-3,8-9H2,(H,10,11)(H,12,13) Key: ILRYLPWNYFXEMH-UHFFFAOYAH
SMILES C(CSC[C@@H](C(=O)O)N)[C@@H](C(=O)O)N
Properties
Chemical formula	C7H14N2O4S
Molar mass	222.26 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Biosynthetically, cystathionine is generated from homocysteine and serine by cystathionine beta synthase (upper reaction in the diagram below). It is then cleaved into cysteine and α-ketobutyrate by cystathionine gamma-lyase (lower reaction).

An excess of cystathionine in the urine is called cystathioninuria.

Cysteine metabolism. Cystathionine beta synthase catalyzes the upper reaction and cystathionine gamma-lyase catalyzes the lower reaction.

Cysteine dioxygenase (CDO), and sulfinoalanine decarboxylase can turn cysteine into hypotaurine and then taurine.^[1] Alternately, the cysteine from the cystathionine gamma-lyase can be used by the enzymes glutamate–cysteine ligase (GCL) and glutathione synthetase (GSS) to produce glutathione.