CBS and myelodysplastic syndrome: In addition to altered MAT2A levels, our proteomics results showed that the downstream enzyme responsible for the conversion of homocysteine to cystathionine (i.e., cystathionine beta synthase or CBS, which catalyzes the first committed step of transsulfuration pathway) was downregulated by 1.8-fold in MDS cells (Supplementary file 2) and confirmed via western blot (Fig. 3b) [97].