Abstract: In order to clarify the bioconversion mechanism of 2-furfurylthiol, we cloned the cystathionine β-lyase gene (Str3) from Saccharomyces cerevisiae G20 and expressed it in Escherichia coli BL21, and we further evaluated the catalytic activity of the recombinant enzyme. With the use of orthogonal array design, the optimized induction conditions for the recombinant strain were determined as follows: temperature 20 ℃, IPTG concentration 0.5 mmol/L, and time 13 h. The recombinant Str3p was harvested after ultrasonic disruption of the cells and purified by Ni column affinity chromatography and its molecular mass was measured to be about 52 kDa. The content of soluble Str3p was up to 1.26 mg/mL, the expression level and the enzymatic activity were increased by about 41.7% and 38.6%, respectively, compared with those before optimization. The recombinant Str3p was capable of catalyzing the degradation of cysteine-furfural conjugate into 2-furfurylthiol. The process was greatly influenced by pH value, and the maximum yield of 2-furfurylthiol of 47 μmol/L was obtained at pH 8.0. This study can provide useful information on biosynthesis of 2-furfurylthiol.

Key words: Saccharomyces cerevisiae, cystathionine β-lyase, heterologous expression, in vitro catalysis, 2-furfurylthiol