The strictly anaerobic bacterium Desulfonispora thiosulfatigenes ferments taurine via sulphoacetaldehyde, which is hydrolysed to acetate and sulphite by sulphoacetaldehyde sulpho-lyase (EC 126.96.36.199). The lyase was expressed at high levels and a two-step, 4.5-fold purification yielded an apparently homogeneous soluble protein, which was presumably a homodimer in its native form; the molecular mass of the subunit was about 61kDa (by SDS/PAGE). The mass was determined to be 63.8kDa by matrix-assisted laser-desorption ionization–time-of-flight (MALDI–TOF) MS. The purified enzyme converted 1mol of sulphoacetaldehyde to 1mol each of sulphite and acetate, but no requirement for thiamine pyrophosphate (TPP) was detected. The N-terminal and two internal amino acid sequences were determined, which allowed us to generate PCR primers. The gene was amplified and sequenced. The DNA sequence had no significant homologue in the databases searched, whereas the derived amino acid sequence indicated an oxo-acid lyase, revealed a TPP-binding site and gave a derived molecular mass of 63.8kDa.