Cystathionine Unit Converter

Cystathionine is an intermediate amino acid formed during the transsulfuration pathway, the metabolic route that converts homocysteine into cysteine. It is produced when the enzyme cystathionine beta-synthase (CBS) combines homocysteine with serine.

Cystathionine is then broken down by another enzyme, cystathionine gamma-lyase (CTH), to produce cysteine. Both enzymes require vitamin B6 in its active form (pyridoxal 5'-phosphate) as a cofactor.

Because cystathionine is a transient metabolite, it normally circulates at very low levels in the blood. Changes in its concentration can reflect problems with B-vitamin status, enzyme function, or sulfur amino acid metabolism.

Cystathionine is produced inside cells, primarily in the liver, when CBS combines homocysteine with serine. It is then converted to cysteine by CTH. Small amounts enter the bloodstream as a normal byproduct of this process.