Cystathionine jS-synthase

In some organisms sulfur incorporation involves homocysteine as an intermediate. In such cases cysteine formation occurs by a transsulfuration reaction, with the intermediate formation of L,L-cystathionine (fig. 21.86). Cystathionine is formed in a simple condensation reaction from serine and homocysteine by cystathionine-jS synthase. 

---