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標題: 愛玉果膠甲基酯酶的醣化修飾之特性分析
Characterization of Glycosylation of an Acidic Pectin Methylesterase in Jelly Fig (Ficus awkeotsang) Achenes
作者: 蕭世良
Eric, S.L.Hsiao
關鍵字: Jelly fig;愛玉;Pectin methylesterase;Glycosylation;果膠甲基酯酶;醣化修飾
出版社: 生物科技學研究所
果膠甲基酯酶 (pectin methylesterase;PME)(EC 乃由愛玉瘦果萃取而得,為愛玉凝結成凍的主要酵素。此酵素在愛玉瘦果果皮中為含量最多的蛋白質,在硫酸十二酯鈉聚丙烯醯胺膠體電泳圖上分子量為38 kDa,其作用機制乃使帶酯基的果膠去甲氧基 (methoxyl residues) 而形成果膠酸 (pectic acid) 。本實驗室目前已得到愛玉果膠甲基酯酶的相對基因,並且使用大腸桿菌表達系統表達此酵素,結果發現經過表達的酵素沒有活性,並發現其分子量比從愛玉瘦果中萃取而來的果膠甲基酯酶小約3 kDa。經研究發現,從愛玉瘦果取得的果膠甲基酯酶是一種醣蛋白 (glycoprotein) ,而與大腸桿菌表達的相比其分子量相差的部份正是在於醣化 (glycosylation) 的有無。進一步研究發現此酵素為N-linked的醣蛋白。

Pectin methylesterase (PME) is the key enzyme responsible for the gelation of jelly curd in the water extract of jelly fig (Ficus awkeotasang) achenes. The molecular mass of jelly fig PME, a major protein in jelly fig achenes, was about 38 kDa estimated by SDS-PAGE. Its major function is to de-esterify the methoxylated pectin into a pectic acid. Previously, a cDNA sequence encoding the PME of jelly fig has been obtained and overexpressed in E. coli. The overexpressed PME in E. coli was smaller than the native PME about 3 kDa, and lack of enzymatic activity. In a preliminary analysis, the PME of jelly fig was found as a glycoprotein, and the difference in molecular weight between the native and overexpressed PME was due to glycosylation. Furthermore, jelly fig PME is an N-linked glycoprotein.
Appears in Collections:生物科技學研究所

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