6. 糖による酵素の熱安定化(セミナー : 生物試料の保存における糖の役割)
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概要
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Thermal stabilizing effect of amorphous matrices of sugars on freeze-dried proteins is investigated, remarking on the relation between the stabilizing effect and the degree of crystallinity of sugars. Several sugars and three enzymes (alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH)) were used. Enzymes were freeze-dried with sugars and stored at 65℃. Stability of freeze-dried enzymes was remarkably improved by addition of trehalose or raffmose. By measurement of X-ray diffractometry (XRD), those sugars were found to form fully amorphous matrix in freeze-dried samples. In contrast, glucose, sucrose, and lactose, which were found to be crystallized, were inferior in stabilizing enzymes. Furthermore, though sucrose showed low stabilizing effect when it was crystalline, it stabilized the enzymes highly when it was amorphous. These results indicate that amorphous matrices of sugars have thermal stabilizing effect. By Fourier Transform Infrared (FT-IR) measurement for samples containing amorphous sucrose and LDH, it was found that hydrogen bond formation between sucrose molecules and LDH was prominent. Moreover, dependence of thermal stabilizing effect of sugars on freezing temperature is discussed. Sucrose and LDH were used, and two type samples different in freezing temperature were prepared. The type A sample frozen at -30℃ showed higher thermal stabilizing effect than the type B sample frozen at -196℃, though sucrose was amorphous in both samples. However, radial distribution function (RDF) obtained by XRD showed that sucrose molecules in the type A sample are arranged more randomly than in the type B sample. Results of FT-IR measurement suggested that the degree of hydrogen bond formation between sugar and LDH is higher in the type A sample. These results suggest that the arrangement of sugar molecules affects the thermal stabilizing effect.
- 低温生物工学会の論文
- 2001-07-30
著者
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