cystathionine

Cystathionine is an amino acid involved in the metabolic pathway of methionine. In the body, methionine is converted into homocysteine, then cystathionine, and finally cysteine, with each step facilitated by a specific enzyme.1

Cystathioninuria is a metabolic disorder where the enzyme responsible for converting cystathionine to cysteine is defective. This leads to high levels of cystathionine in the urine. While often mild, it can sometimes be associated with intellectual disability. Treatment with vitamin B6 can be effective in some cases.1

Homocystinuria is another related disorder where the enzyme converting homocysteine to cystathionine is defective. This results in elevated levels of homocysteine and methionine in the blood. Symptoms can include intellectual disability, vision problems, skeletal deformities, and blood clots.2