Abstract：
Difructose anhydride I (DFA-I) can be produced from inulin, with DFA-I-forming inulin fructotransferase (IFTase-I). However, the metabolism of inulin through DFA-I remains unclear. To clarify this pathway, several genes of enzymes related to this pathway in the genome of Microbacterium flavum DSM 18909 were synthesized, and the corresponding enzymes were encoded, purified, and investigated in vitro. After inulin is decomposed to DFA-I by IFTase-I, DFA-I is hydrolyzed to inulobiose by DFA-I hydrolase. Inulobiose is then hydrolyzed by β-fructofuranosidase to form fructose. Finally, fructose enters glycolysis through fructokinase. A β-fructofuranosidase (MfFFase1) clears the byproducts (sucrose and fructo-oligosaccharides), which might be partially hydrolyzed by fructan β-(2,1)-fructosidase/1-exohydrolase and another fructofuranosidase (MfFFase2). Exploring the DFA-I pathway of inulin and well-studied enzymes in vitro extends our basic scientific knowledge of the energy-providing way of inulin, thereby paving the way for further investigations in vivo and offering a reference for further nutritional investigation of inulin and DFA-I in the future.
摘要：
二果糖酸酐I（DFA-I）可以由菊粉生产，与DFA-I形成菊粉果糖转移酶（IFTase-I）。然而,菊粉通过DFA-I的代谢仍不清楚。为了澄清这条道路，合成了黄微杆菌DSM18909基因组中与该途径相关的几个酶基因，相应的酶被编码，纯化,并在体外进行了研究。菊粉通过IFTase-I分解为DFA-I后，通过DFA-I水解酶将DFA-I水解为氟尿糖。然后通过β-呋喃果糖苷酶水解红外二糖以形成果糖。最后,果糖通过果糖激酶进入糖酵解。β-呋喃果糖苷酶（MfFase1）清除副产物（蔗糖和低聚果糖），可能被果聚糖β-（2,1）-果糖苷酶/1-外水解酶和另一种呋喃果糖苷酶（MfFase2）部分水解。探索菊粉的DFA-I途径和体外研究良好的酶扩展了我们对菊粉能量提供方式的基本科学知识，从而为进一步的体内研究铺平了道路，并为将来菊粉和DFA-I的进一步营养研究提供了参考。
