Description_x000D_ Biochem/physiol Actions_x000D_ DL-Propargylglycine (PAG) is an irreversible inhibitor of the enzyme cystathionine γ-lyase (GCL), a key enzyme involved in glutathione synthesis and the metabolic transsulfuration pathway which regulates homocysteine concentration and mediates cysteine synthesis. Treatment of animal disease models with PAG was shown to alleviate symptoms of diseases that impair the formation or action of hydrogen sulfide (H2S).