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).

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.

References

  1. ^ Harris Ripps, Wen Shen (2012). "Review: Taurine: A "very essential" amino acid". Molecular Vision. 18: 2673–2686. PMC 3501277. PMID 23170060.