Question: Please describe this drug.
 The Chemical has the SMILES N[C@@H](CCSC[C@H](N)C(=O)O)C(=O)O.
Answer: Cystathionine is a metabolite found in or produced by Escherichia coli (strain K12, MG1655).
{#Question|Q!}: {quest#}
{#Constraint:|Description:|!} The {#Molecule|Compound|Chemical!} {#has the|can be represented with the!} {SMILES__description} {SMILES#}.
{#Answer|Result|Answer!}: {answ#}
N[C@@H](CCSC[C@H](N)C(=O)O)C(=O)O
C(CSC[C@@H](C(=O)O)N)[C@@H](C(=O)O)N
(2S)-2-amino-4-[(2R)-2-amino-2-carboxyethyl]sulfanylbutanoicacid
Please describe this drug.