Cloning and characterisation of a cystathionine β/γ-lyase from two Oenococcus oeni oenological strains.

Sulphur-containing compounds in wine have been extensively studied because of their effect on wine flavour and quality. In this study, an enzyme that degrades sulphur-containing amino acids was cloned and characterised from two Oenococcus oeni strains of oenological origins. The enzyme has features of a cystathionine-γ-lyase (EC 4.4.1.1), a pyridoxal-5-phosphate-dependent enzyme catalysing an α,γ-elimination reaction of L: -cystathionine to produce L: -cysteine, α-ketobutyrate and ammonia. Moreover, it was able to catalyse an α,β-elimination reaction producing homocysteine, pyruvate and ammonia from L: -cystathionine. An elimination reaction of L: -cysteine and DL: -homocysteine was also efficiently catalysed by the enzyme, resulting in the formation of hydrogen sulphide. Furthermore, the ability to demethiolate methionine into methanethiol, an unfavourable volatile sulphur compound in terms of wine aroma, was observed. The findings of this work suggest that O. oeni seems to play a minor role in the production of volatile sulphur compounds during the vinification process as the optimal conditions were far from the harsh wine environment.