Sulphoacetaldehyde sulpho-lyase (EC 4.4.1.12) from Desulfonispora thiosulfatigenes: purification, properties and primary sequence

The strictly anaerobic bacterium Desulfonispora thiosulfatigenes ferments t aurine via sulphoacetaldehyde, which is hydrolysed to acetate and sulphite by sulphoacetaldehyde sulpho-lyase (EC 4.4.1.12). The lyase was expressed a t high levels and a two-step, 4.5-fold purification yielded an apparently h omogeneous soluble protein, which was presumably a homodimer in its native form the molecular mass of the subunit was about 61 kDa (by SDS/PAGE). The mass was determined to be 63.8 kDa by matrix-assisted laser-desorption ioni zation-time-of-flight (MALDI-TOF) MS. The purified enzyme converted I mol o f sulphoacetaldehyde to I mol each of sulphite and acetate, but no requirem ent for thiamine pyrophosphate (TPP) was detected. The N-terminal and two i nternal 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 63.8 kDa.