Study on the New Enzymatic System For the Formation of Citral as the Biologically Active Substance

在日本，新鲜的未成熟的和成熟的生姜根茎都被用于各种菜肴。但未成熟姜与成熟姜的主要风味成分存在差异。前者主要含有香叶醇和乙酸香叶醇，而柠檬醛（香叶醛和丁香醛）的浓度在成熟姜中显著增加，尤其是香叶醛。本研究首次发现生姜根茎中存在对葡萄糖苷和半乳糖苷具有特异性的葡萄糖苷酶活性。此外，还首次证实了乙醇脱氢酶（ADH）的活性。生姜的ADH依赖于NADP，最适pH为9.0。它还显示了对香叶醇的特异性。研究了生姜生长和贮藏过程中生成的老年虫数量与ADH活性的关系，以阐明成熟和贮藏过程中老年虫含量增加的机理。贮藏30 d后，geranial的含量达到最大值，之后略有下降或保持不变。上述酶活性的变化与微生物的形成过程基本一致。由此可见，姜中抗利尿激素（ADH）活性对姜中老年虫的形成有一定的影响。为了更有效地利用生姜的根茎，必须对ADH进行纯化和鉴定。

In Japan both of fresh immature and mature rhizomes of ginger are used for various dishes. But the main flavor compounds are different between immature ginger and mature one. The former contains geraiol and geranyl acetate mainly, in contrast the concentration of citral (geranial and neral), especially geranial are increased dramatically in the mature ginger. In this study, it was found for the first time that the rhizomes of ginger have glucosidase activity which has the specificity for glucoside and galactoside. In addition, alcohol dehydrogenase (ADH) activity was also comfirmed for the first time. And the ADH of ginger was dependent of NADP and the optimum pH is 9.0. It also showed the specificity for geraniol. We also investigated the relationship between the quantitiy of geranial formed and the ADH activity during growth and storage of ginger to clarify the mechanism for the increase in content og geranial in maturing and stored ginger. The amounts of geranial reached the maximum after 30 days of storage, and after that slightly decreased or remained constant. The change of the enzyme activities above was parallel well to the geranial formation. From these results, it was concluded that ADH activity of ginger would influence the formation of geranial in ginger. the purification and characterization of ADH should be accomplished to use the rhizomes of ginger more effectively.