Cystathionine

    Transsulfuration is the primary pathway for irreversible disposal of homocysteine ​​and begins by replacing a serine hydroxyl group with a sulfhydryl group to form cystathionine using the enzyme cystathionine β-synthase (CBS). This reaction requires nutrient cofactors such as vitamin B6 and iron. Cystathionine is a dipeptide that is then converted to cysteine ​​using the enzyme cystathionine gamma-lyase (CTH). Currently, there is no known source or physiological function for cystathionine other than serving as a transsulfuration intermediate. Some literature suggests that cystathionine may exert protection against endoplasmic reticulum stress-induced tissue damage and cell death, but studies are scarce. 103 Because cystathionine is an intermediate of the transsulfuration pathway, elevation of this biomarker may indicate a backup of the transsulfuration pathway. The conversion of cystathionine to glutathione requires necessary cofactors such as vitamin B6, zinc, glycine, and magnesium. Therefore, transient elevations of this metabolite may indicate an increased need for these cofactors.

 

Low cystathionine:

- Vitamin B6 cofactor required for CBS enzyme

High cystathionine:

- CBS SNP

- Elevated SAM which directly upregulates CBS enzyme

- GDM, betaine supplementation

- High oxidative stress or inflammation

- Vitamin B₆ cofactor required for CTH enzyme