Gamma-cystathionase (CTH)

CSE is an enzyme which breaks down cystathionine into cysteine and alpha-ketobutyrate. Pyridoxal phosphate is a prosthetic group of this enzyme.The bioavailability of cysteine is rate-limiting for the hepatic synthesis of glutathione. Cysteine is provided through either the diet or the transsulfuration pathway, in which cystathionine derived from methionine is transformed into cysteine by cystathionine gamma-lyase.Mutant mice lacking CTH displayed pronounced hypertension and diminished endothelium-dependent vasorelaxation. Cystathionine was physiologically activated by calcium and calmodulin , which is a mechanism for H2S formation in response to vascular activation. Yang et al. (2008) concluded that their findings provided direct evidence that H2S is a physiologic vasodilator and regulator of blood pressure.