It cleaves a carbon-sulfur bound releasing sulfide and the unstable enamine product 2-aminoprop-2-enoate that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and ammonia. The reaction can be catalysed by other pyridoxal-phosphate proteins (cf. EC 4.4.1.1, cystathionine γ-lyase).
The enzyme from the archaeon Methanocaldococcus jannaschii contains a [4Fe-4S] cluster instead of PLP.
The validated PLP-dependent enzymes that catalyze this reaction also show cystathionine beta-lyase activity (E.C. 4.4.1.8) and sometimes methionine gamma-lyase activity (4.4.1.11).