「納豆激酶」是一種絲胺酸型枯草桿菌類鹼性蛋白酶，主要是由微生物醱酵後所附在大豆表面的拉絲黏稠物質所組成，目前被廣泛應用於「保健食品」中。許多學者研究指出納豆激酶具有提高血漿中血纖維蛋白酶之水解活性，且可直接水解血纖維蛋白。

本研究的主要目的為探討以液態醱酵培養方式所產生之納豆激酶及其功效評估。研究方法則有菌株之基本特性測試、不同納豆激酶劑量與血栓平板檢測準確度分析、利用快速蛋白質液相層析儀(FPLC，Fast Protein Liquid Chromatography)從納豆醱酵液中純化出納豆激酶及納豆激酶體外溶解血栓之動物測試（大白鼠口服），到最終的製作納豆激酶抗體(兔子)並利用蛋白質轉漬分析（western blot）等方式驗證該酵素是可以經腸、胃的吸收進入血液中。

研究發現納豆菌之液態醱酵是以饋料培養方式優於一般批次培養方式，在比較其產生之納豆生菌數及激酶值方面，前者分別優於後者約3.95及2.9倍，而在大白鼠經口服納豆膠囊內容物後，發現在口服後第2小時可達最佳吸收效果，但是在8小時後降解。另外，其酵素動力學參數檢測值Km及Vmax則分別為0.926 mM及236 mM/hr。

結論則是預防慢性病雖已成為國內外積極進行的重要研發項目，但其預防之道往往仍須藉由日常飲食與生活作息之改變開始，而將納豆菌醱酵食品(Natto fermented foods)融入日常飲食似乎是其中最簡易之預防方法之一；雖然研究發現納豆激酶可以作為預防血栓及其相關疾病之投遞藥物；但是，由於納豆激酶是屬於體外蛋白質，長期食用是否會對人體造成過敏等現象，仍需要進一步的確認。

Nattokinase (NK) , a serine family subtilisin-like alkaline protease existing in the sticky cheese-like secreted by subtilis Natto on the surface of fermented soybean , has been widely applied to health-care food now. The enzyme has a high ability to degraded fibrin or activated plasminogen on the fibrinolytic system .

In order to evaluate the physicochemical properties of the NK enzyme , liquid cultivation method and the transport mechanism of NK acrossing the rat intestinal tract into blood vessel have been explored and the experiments , such as enzyme activity test、the fibrin plate method for estimating fibrinolytic activity、purification of NK by FPLC from fermentation broth ﹑the parameters of enzyme kinetics measured by UV-vistable streptophotometer and detection of NK in the plasma from blood samples drawn at intervals after rat oral administration of the enzyme by Sodium dodecyl sulfate - Polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting analysis with an anti-NK antibody have been carried out .

The results thus obtained suggested that production of the unit of NK activity and Natto bacteria count by liquid cultivation in fed-batch is better than batch culture. NK was absorbed from the rat intestinal tract and the highest absorption was ～2 hr after oral administration of the enzyme , and it was degraded after 8 hr . The parameters of enzyme kinetics measured showed that the Km=0.926 mM and Vmax is 236 mM/hr .

Although NK is a potent fibrinolytic enzyme , which can be mass produced by liquid cultivation , it is also a potential drug for use in the treatment of embolism in the prevention of the disease. Nevertheless , it is still an extraneous protein , whether it will induce allergy in vivo is still under investigation .

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