Homocystine

Homocystine is a sulfur-containing amino acid formed by the oxidative dimerization of two homocysteine molecules via a disulfide bond [1.4.3]. It serves as a critical metabolic intermediate in the methionine-homocysteine cycle, where its levels are tightly regulated by enzymes such as cystathionine beta-synthase (CBS) and methylenetetrahydrofolate reductase (MTHFR) [1.2.3]. While homocystine itself is not a traditional therapeutic target like a receptor or enzyme, it is a primary pathological biomarker; elevated concentrations in the blood and urine (homocystinuria) are indicative of metabolic disorders that lead to severe clinical outcomes [1.1.2, 1.2.1]. These outcomes include premature atherosclerosis, thromboembolism, lens dislocation, and skeletal abnormalities [1.1.2, 1.3.2]. Therapeutic management focuses on lowering homocystine levels by administering cofactors such as pyridoxine (Vitamin B6), cobalamin (Vitamin B12), and folic acid, which enhance the activity of the remaining functional enzymes, or by using betaine to facilitate the remethylation of homocysteine to methionine [1.1.2, 1.3.3]. Consequently, homocystine is a central focus for clinical monitoring and the primary endpoint for evaluating the efficacy of dietary and pharmacological interventions in patients with sulfur amino acid metabolism disorders [1.4.1].

Other names

L-Homocystine4,4'-disulfanediylbis(2-aminobutanoic acid)Homocysteine disulfide

Metabolic reduction of plasma levels via enzymatic cofactor supplementation (e.g., CBS or MTHFR pathways) [1.1.2, 1.2.3].