醇脱氢酶同工酶基因表达与酿酒酵母催化2-辛酮不对称还原的关系

Relationship between Gene Expression of ADH Isozymes and Asymmetric Reduction of 2-Octanone with Saccharomyces cerevisiae

以Ⅱ型酿酒酵母为催化剂、2-辛酮为底物、水/正十二烷两相体系为反应体系,考察了有机介质处理对酿酒酵母ADH 1~3同工酶基因表达水平的影响及其与催化2-辛酮不对称还原反应特性的关联性.结果表明,酿酒酵母细胞经不同有机介质分别处理后,部分醇脱氢酶(ADH)同工酶基因的表达水平发生明显变化,酵母细胞催化2-辛酮不对称还原反应的特性也不同.甲苯和2-辛醇处理严重抑制ADH 1基因的表达,而正十二烷、正辛烷和正己烷处理对ADH 1基因表达影响不大,但2-辛酮处理使ADH1基因的表达水平大幅度提高;甲苯和2-辛醇处理使ADH 2基因的表达水平大幅提高,但正十二烷、正辛烷、正己烷和2-辛酮处理抑制ADH 2基因的表达.抑制ADH 1的基因表达可能使催化2-辛酮不对称还原反应催化活性降低,而抑制ADH 2的表达则可提高细胞催化不对称还原的选择性.未发现ADH 3基因表达与酵母催化活性和反应选择性之间的关联,表明ADH 1是催化底物2-辛酮不对称还原的主要同工酶,且具有良好的对映选择性,而ADH 2对2-辛酮的不对称还原的对映选择性不佳.

In the water/n-dodecane biphasic reaction system, the influence of organic solvent treatment on the gene expression level of isozymes of alcohol dehydrogenase （ADH） 1-3 was investigated to probe their correlation in asymmetric reduction of the substrate 2-octanone by Saccharomyces cerevisiae type II. The results showed that after treatment with organic media, the relative expression level of isozymes of alcohol dehydrogenase （ADH） varied, along with the different properties shown in asymmetric reduction of 2-octanone treatmented by Saccharomyces cerevisiae, the gene expression level of ADH 1 was severely inhibited by toluene and 2-octanol, but it was not obviously influenced by n-dodecane, n-octane and n-hexane, while substantially enhanced by 2-octanone. However, the gene expression level of ADH 2 was highly increased by toluene and 2-octanol, but inhibited by n-dodecane, n-octane, n-hexane, and 2-octanone. Furthermore, the inhibition of ADH 1 gene expression would reduce the catalytic activity, and inhibition of ADH 2 gene expression would improve the enantiomeric selectivity, while the gene expression level of ADH 3 would not influence both the activity and selectivity. The isozyme ADH 1 which has good enantio selectivity is the key oxidoreductase for catalyzing asymmetric reduction of 2-ocatnone by Saccharomyces cerevisiae type II, and the isozyme ADH 2 is of poor enantio selectivity while it conducts the same reaction.