Investigation on Molecular Mechanism of Sucrose-degrading Enzyme in Asian Honeybee.

我们分析了欧洲蜜蜂的三种蔗糖降解同工酶（α-葡萄糖苷酶I，II和III），因为这些酶对高浓度蔗糖表现出有趣的活性。α-葡萄糖苷酶I是一种独特的变构酶，在极高的蔗糖浓度下表现出负协同性。α-葡萄糖苷酶II也表现出正协同的变构性质。α-葡萄糖苷酶III是一种michaelis - menten型酶，分泌到花蜜（蜜蜂从花中采集）中，并有助于蜂蜜的形成。本课题的目的是：1)亚洲蜜蜂体内存在变构α-葡萄糖苷酶，2)研究成蜜机制，3)三种α-葡萄糖苷酶同工酶的表达调控。本研究调查了四种蜜蜂。从典型的亚洲蜜蜂（生活在泰国、韩国和日本）中，用色谱法分离到了3个同工酶。其中一种是与欧洲蜜蜂α-葡萄糖苷酶I具有相似性质的变构酶，可以进行负协同性的分子分析。第二种酶为α-葡萄糖苷酶ii型同工酶。对蜂蜜中的酶进行了研究，发现与α-葡萄糖苷酶iii型同工酶相似。克隆了这三种酶的cdna。结果发现，三种同工酶的表达受到调控。在泰国小蜜蜂中也发现了3种α-葡萄糖苷酶，其中分离到2种α-葡萄糖苷酶。它们的性质与α-葡萄糖苷酶I和α-葡萄糖苷酶II几乎相同。将蜂蜜中的酶与成蜂的酶进行了比较。本课题研究的所有蜜蜂品种均含有变构酶。亚洲蜜蜂可分为具有3种α-葡萄糖苷酶同工酶和具有2种α-葡萄糖苷酶同工酶两种类型。最近，我们发现大黄蜂也有两种α-葡萄糖苷酶同工酶。进一步的研究将阐明蜜蜂蔗糖降解酶的分子机制。少

We have analyzed three sucrose-degrading isozymes (α-glucosidase I,II, and III) in European honeybees, since these enzymes exhibited the interesting activity to sucrose of high concentration. α-Glucosidase I was a unique allosteric enzyme to display negative cooperativity in extremely high sucrose concentration. α-Glucosidase II also exhibited the allosteric property of positive cooperativity. α-Glucosidase III was a Michaelis-Menten-type enzyme to be secreted to nectar (bees gathered from flower) and to contribute to the formation of honey. Purpose of this project is i)existence of allosteric α-glucosidase in Asian honeybees, ii)investigation of honey-forming mechanism, and iii)regulation in expression of three α-glucosidase isozymes.Four kinds of honeybee species were investigated in this research. From typical Asian honeybees (living in Thailand, Korea and Japan), three isozymes were isolated by chromatographic method. One of them was an allosteric enzyme having similar properties t … More o European honeybee α-glucosidase I, allowing to molecular analysis of negative cooperativity. The second enzyme was α-glucosidase II-type isozyme. Enzyme in honey was also investigated, and showed similar to one of enzymes (α-glucosidase III-type isozyme). cDNAs of these three enzyme were cloned. It was found that the expression of three isozymes was regulated. In small honeybees living in Thailand, three α-glucosidases were also found, in which two α-glucosidases were isolated. Their properties investigated were almost identical to those of α-glucosidases I and II. Enzyme in honey was compared with adult bee enzymes. All honeybee species studied in this project contained allosteric enzyme. Asian honeybees were divided into two types : i)having three α-glucosidase isozymes and ii)having two α-glucosidase isozymes. Recently, we found that bumblebees also had two α-glucosidase isozymes. Further research will elucidate the interesting molecular mechanism of sucrose-degrading enzymes in flower bees. Less