Cystathionine gamma-lyase/CTH Protein, Human

Cystathionine gamma-lyase (CTH) plays a crucial role in the final step of the trans-sulfuration pathway, converting L-methionine to L-cysteine in a pyridoxal-5'-phosphate (PLP)-dependent manner. This process involves cleaving L,L-cystathionine into L-cysteine, ammonia, and 2-oxobutanoate. A portion of the L-cysteine produced through this pathway is utilized for the biosynthesis of the antioxidant glutathione. Beyond its role in L-cystathionine conversion, CTH functions as a cysteine-protein sulfhydrase, mediating sulfhydration of specific cysteine residues in target proteins like GAPDH, PTPN1, and NF-kappa-B subunit RELA, thereby regulating their function. Moreover, CTH utilizes L-cysteine and L-homocysteine to produce the gasotransmitter hydrogen sulfide (H2S), a signaling molecule implicated in various physiological processes such as vasodilation, bone protection, and inflammation. Under conditions of severe hyperhomocysteinemia, CTH can convert L-cysteine and L-homocysteine into lanthionine and homolanthionine, structural homologs of L,L-cystathionine. Additionally, CTH contributes to myogenesis by facilitating H2S biogenesis in skeletal muscle tissue and can accept homoserine as a substrate. Furthermore, it catalyzes the elimination of selenocystathionine to yield selenocysteine, ammonia, and 2-oxobutanoate, a process relevant to dietary selenium metabolism.