Cystathionine Gamma-Lyase (CTH) belongs to the trans-sulfuration enzymes family. CTH exists as a homotetramer and interacts with CALM in a calcium-dependent manner. CTH breaks down cystathionine into cysteine, ammonia and 2-oxobutanoate. CTH catalyzes the last step in the trans-sulfuration pathway from methionine to cysteine and has broad substrate specificity. Defects in CTH will lead to cystathioninuria, which is an autosomal recessive phenotype characterized by abnormal accumulation of plasma cystathionine.