QS412透性化细胞产海藻糖特性研究

Use of permeabilized Micrococcus roseus QS412 cells in trehalose production

透性化细胞中在麦芽寡糖基海藻糖合成酶和麦芽寡糖基海藻糖水解酶作用下由淀粉生产海藻糖,其使用可省略酶的纯化和胞内酶的固定化。本文研究了金属离子对透性化细胞产海藻糖活性的影响,观察到Mg2+对其活性有提高作用,Zn2+、Mn2+、Cu2+、Fe2+、Hg2+5种2价离子对其活性有明显抑制作用。其中,Hg2+的抑制作用最为明显,而Mn2+的作用未见报道。Zn2+在40 mmol/L浓度以上能完全抑制体系中MTHase的活性,并且这种抑制作用可以通过添加EDTA消除,这就提供了制备MTHase底物及在两种酶存在下单独测定MTSase活性的可能。本征动力学和宏观动力学分析表明透性化细胞合成海藻糖的过程中外扩散影响可忽略,内扩散影响显著。通过对该过程作用特性的研究,为透性化细胞的研究和使用打下进一步的基础。

Permeabilized Micrococcus roseus QS412 cells have been used to produce trehalose from starch through catalysis by maltooligosyl trehalose synthase and maltooligosyl trehalose trehalohydrolase present in the cells, Use of permeabilized cells allows the conventional enzyme purification and immobilization steps to be omitted and simplifies the synthesis procedure. The trehalose synthase activity of the permeabilized cells was found to be increased by addition of Mg^2＋ , but was inhibited by Zn^2 ＋ , Mn^2＋, Cu^2 ＋ , Fe^2 ＋ and Hg^2＋ . The effect of Hg^2＋ was particularly marked and the influence of Mn^2 ＋ has not been previously reported. It was found that the presence of Zn^2 ＋ with a concentration of 40 mmmol/L completely inhibited the trehalose biosynthesis ability of permeabilized cells and that this inhibition effect could be eliminated by sequestration of the metal cations with EDTA. This allowed the MTHase substrate to be produced and the MTSase activity to be determined within the permeabilized cells. A kinetic analysis showed that internal diffusion played a prominent role in the intracellular synthesis of trehalose.