44 グルコノアミジン型阻害剤による就眠運動の鍵酵素β-グルコシダーゼのアフィニティー精製(口頭発表の部)

Nyctinastic movement of leguminous plants is controlled by the glucosylated leaf-movement factor, whose concentration changes throughout the day, regulated by β-glucosidase. Therefore, in order to understand the controlling mechanism of the movement by circadian clock, purification of this key enzymeis essential. Many isozymes of β-glucosidase are known to exist in plant body. To purify the key enzyme from this mixture, affinity chromatography is a powerful tool. We have tried two affinity gel 4 and 5, which is an usual tool used for purification of β-glucosidase. But they were both not effective, from the luck of aglycon part or the low inhibition constant. According to this experiment, we concluded that affinity ligand should be an analog of the leaf-movement factor, and at the same time it should be a strong inhibitor. Gluconoamidine is known to show strong inhibition toward β-glucosidase. Thus, we have planed to synthesize 7, an analog of leaf-movement factor with gluconoamidine part, instead of glucose as the glucoside part. Several methods are known for the synthesis of gluconoamidine compound using thionolactam(6) and amine compound. But there are several restriction. 1) Benzyl protected sugar derivative are necessary 2) Needs of a reactive amine group. And also, in some cases the epimerization at C2 of the sugar moiety occurs. To overcome these restrictions, we have developed a novel method for the synthesis of gluconoamidine compound. And by employing this method we have synthesized 7. Compound 7 showed strong and selective inhibition toward commercially available β-glucosidase. Encouraged by this result we synthesized an affinity gel 16, using 7 as a ligand. Purification of the crude enzyme, extracted from Lespedeza cuneata, by affinity gel 16 was effective. We are now working on further purification of the key enzyme.