Cystathionine β-lyase (CBL) catalyses the PLP-dependent β-elimination of cystathionine, yielding homocysteine, pyruvate and ammonia, while the γ-elimination of this pseudosymmetric substrate by cystathionine γ-lyase (CGL) produces cysteine, α-ketobutyrate and ammonia. The distinct β versus γ-elimination reaction specificity of the structurally conserved eCBL and yCGL enzymes provides an ideal system to probe the subtle factors that regulate activity and specificity. Studies exploring these factors will enable the continued development of our vi