Enzymatic production of aroma compound 3-mercapto-1-hexanol enantiomers via cysteine-S-conjugate β-lyase

Abstract

3-Mercapto-1-hexanol (3 MH) has been identified as the primary compound responsible for fruity aromas in Sauvignon blanc wines. The two enantiomers of 3 MH, (R)-3MH and (S)-3MH, have distinct odor characteristics. However, the enzymatic conversion of these two enantiomers has not been investigated. In this study, cysteine monoadduct diastereomers were successfully isolated to obtain the desired pure product using flash chromatography with normal-phase silica gel and an appropriate solvent system. The protein sequence of cysteine-Sconjugate beta-lyase MetC from Photobacterium damselae was analyzed, and a three dimensional structure model was constructed using comparative modeling. The optimum pH and temperature for (3-lyase activity of Ph. damselae MetC were determined, and MetC exhibited the highest beta-lyase activity at 30 degrees C and pH 9. MetC demonstrated Michelis-Menton kinetics for the substrates L-Cystine and L-Cystathionine, with specific constants of 9.5 x 104 and 9.3 x 104 M-1S-1, respectively, whereas it showed sigmoidal kinetics for cysteine monoadduct 3 MH diastereomers with negative cooperativity. Furthermore, 3 MH was generated from its precursor by MetC, and the conversion rate was calculated. This study characterizes Ph. damselae MetC and provides a practical approach for using cysteine-S-conjugate beta-lyase in the production of 3 MH enantiomers.