Relative Contributions of Cystathionine β-Synthase and γ-Cystathionase to H2S Biogenesis via Alternative Trans-sulfuration Reactions

In mammals, the two enzymes in the trans-sulfuration pathway, cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), are believed to be chiefly responsible for hydrogen sulfide (H2S) biogenesis. In this study, we report a detailed kinetic analysis of the human and yeast CBS-catalyzed reactions that result in H2S generation. CBS from both organisms shows a marked preference for H2S generation by β-replacement of cysteine by homocysteine....