What is "cystathionine"

n. (context biochemistry English) An intermediate, ''2-amino-4-(2-amino-2-carboxy-ethyl) thio-butanoic acid'', in the biosynthesis of cysteine

Cystathionine is an intermediate in the synthesis of cysteine.

An excess in the urine is called cystathioninuria.

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).