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

在日本，生姜的新鲜未成熟和成熟的根茎都用于各种菜肴。但嫩姜和成熟姜的主要风味物质有所不同。前者主要含有香叶醇和乙酸香叶酯，而成熟姜中柠檬醛（香叶醛和橙花醛），特别是香叶醛的含量显著增加。本研究首次发现生姜根茎具有糖苷酶活性，且对葡萄糖苷和半乳糖苷具有专一性。此外，还首次测定了乙醇脱氢酶（ADH）活性。生姜的ADH依赖于NADP，最适pH为9.0。对香叶醇也有特异性。并研究了生姜生长和贮藏过程中香叶醛形成量与ADH活性的关系，以阐明生姜成熟和贮藏过程中香叶醛含量增加的机理。香叶醛含量在贮藏30 d后达到最大值，30 d后略有下降或保持不变。上述酶活性的变化与香叶醛的形成有较好的平行性。由此可见，生姜中ADH的活性对老鹳草醛的形成有一定的影响。为了更有效地利用生姜根茎，需要进一步研究ADH的纯化和性质。

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.