Cystathionine

Key intermediate in the trans-sulfuration pathway from methionine to cysteine.

Cystathionine
IUPAC name	2-amino-4-(2-amino-2-carboxy-ethyl) thio-butanoic acid
Identifiers
CAS number	[56-88-2]
PubChem	834
MeSH	Cystathionine
SMILES	C(CSCC(C(=O)O)N)C(C(=O)O)N
ChemSpider ID	811
Properties
Molecular formula	C7H14N2O4S
Molar mass	222.263 g/mol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Cystathionine is an intermediate in the synthesis of cysteine.

It is generated from homocysteine and serine by cystathionine beta synthase.

It is cleaved into cysteine and α-ketobutyrate by cystathionine gamma-lyase.

An excess in the urine is called cystathioninuria.

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

v • d • e Amino acid metabolism metabolic intermediates K→acetyl-CoA lysine→ Saccharopine · Allysine · α-Aminoadipic acid · α-Aminoadipate · Glutaryl-CoA · Glutaconyl-CoA · Crotonyl-CoA · β-Hydroxybutyryl-CoA leucine→ α-Ketoisocaproic acid · Isovaleryl-CoA · 3-Methylcrotonyl-CoA · 3-Methylglutaconyl-CoA · HMG-CoA tryptophan→alanine→ N'-Formylkynurenine · Kynurenine · Anthranilic acid · 3-Hydroxykynurenine · 3-Hydroxyanthranilic acid · 2-Amino-3-carboxymuconic semialdehyde · 2-Aminomuconic semialdehyde · 2-Aminomuconic acid · Glutaryl-CoA G G→pyruvate→citrate glycine→serine→ 3-Phosphoglyceric acid glycine→creatine: Glycocyamine · Phosphocreatine · Creatinine G→glutamate→ α-ketoglutarate histidine→ Urocanic acid · Imidazol-4-one-5-propionic acid · Formiminoglutamic acid · Glutamate-1-semialdehyde proline→ 1-Pyrroline-5-carboxylic acid arginine→ Ornithine · Putrescine · Agmatine other cysteine+glutamate→glutathione: γ-Glutamylcysteine G→propionyl-CoA→ succinyl-CoA valine→ α-Ketoisovaleric acid · Isobutyryl-CoA · Methacrylyl-CoA · 3-Hydroxyisobutyryl-CoA · 3-Hydroxyisobutyric acid · 2-Methyl-3-oxopropanoic acid isoleucine→ 2,3-Dihydroxy-3-methylpentanoic acid · 2-Methylbutyryl-CoA · Tiglyl-CoA · 2-Methylacetoacetyl-CoA methionine→ generation of homocysteine: S-Adenosyl methionine · S-Adenosyl-L-homocysteine · Homocysteine conversion to cysteine: Cystathionine · alpha-Ketobutyric acid+Cysteine threonine→ α-Ketobutyric acid propionyl-CoA→ Methylmalonyl-CoA G→fumarate phenylalanine→tyrosine→ 4-Hydroxyphenylpyruvic acid · Homogentisic acid · 4-Maleylacetoacetate G→oxaloacetate see urea cycle Other Cysteine metabolism Cysteine sulfinic acid see also enzymes, disorders

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