Furthermore, the same group discovered that ischemic stroke altered the expression of enzymes involved in Hcy metabolisms, such as cystathionine-β-synthase (CBS), cystathionine gamma-lyase (CSE), methylenetetrahydrofolate reductase (MTHFR), and S-adenosyl-L-homocysteine hydrolase (SAHH) (Figure 4). The gene discussed is MTHFR; the disease is ischemic stroke.