摘要或動機

植物合成澱粉?抑制劑可以對抗動物的取食，國外實驗證明數種澱粉?抑制劑對害蟲防 治具有顯著效果，其中以腰豆(Phaseolus vulgaris)研究最多。我們利用5% T.C.A.進行粗萃，從台灣常見豆類中篩選出四季豆(與腰豆同種不同品系)與菜豆，對麗蠅的澱粉?具有明顯的抑制效果，對豬胰臟與黃豆澱粉?的抑制效果則小或無，此種抑制特異性深具害蟲防治的潛力。經由溫度與pH 的試驗發現粗萃中的澱粉?抑制劑成分應為蛋白質。我們以四季豆作為繼續研究的對象，將粗萃進一步純化，經由陰離子交換與膠體過濾層析，分離出單一蛋白質，經蛋 白質定序比對確認其可能為國外發表的腰豆澱粉?抑制劑—αAI-1。經由測試發現此抑制劑在 85℃時仍能抑制果蠅澱粉?，為一相當穩定的蛋白質；且抑制劑的作用受pH 值影響很大，在偏酸性環境下的效果最好，與昆蟲分泌澱粉?的部位亦為酸性環境有相當密切的關聯；且其 抑制作用具特異性，可明顯抑制果蠅、入侵紅火蟻、白蟻、蟑螂及麵包蟲等昆蟲的澱粉?活性，對人類唾液、豬胰臟、四季豆本身及黃豆澱粉?的抑制效果很小或無，值得繼續深入研究。 Plant amylase inhibitors can fight against predation from plant-eating animals. It has been reported that several amylase inhibitors have an obvious effect on pest control; among them that from Phaseolus vulgaris got the most surveyed. 5% T.C.A was employed to make crude extracts. We have screened the amylase inhibitor activities from crude extract among beans common in Taiwan. The inhibitors from both string beans (the different strain of Phaseolus vulgaris) and cowpea notably inhibited the amylases in Chrysomia megacephala, but little or no inhibition in porcine pancreas and soy bean. This specific inhibition behavior suggested strong potential in pest control. Its activity can be affected by temperature and pH suggested that amylase inhibitors in crude extracts should be proteins. String beans were chosen to be further purified from the crude extracts. A single protein was isolated after ion exchange and gel filtration chromatography. Through protein sequencing, the partial amino acid sequences were highly homologous to that ofαAI-1 from Phaseolus vulgaris, indicating it might beαAI-1. The purified protein still can inhibit the amylase from Drosophila melanogaster at 85℃, suggesting it is thermal-stable. Its activity was affected by pH and reached the peak in weak acidic environment, which might be related to the fact that amylases are secreted in acidic environment of insect’s midgut. It obviously inhibited the amylases from D. melanogaster,Solenopsis invicta, Odontotermes formosanus, Periplaneta Americana Linnaeus, and Alphitobius sp., while not to human saliva, porcine pancreas, soy bean and string beans itself. The unique pattern of inhibition activities of the purified amylase inhibitor was worthy of further anlysis.