Yamashita H, Theerasilp S, Aiuchi T, Nakaya K, Nakamura Y, Kurihara Y
Department of Chemistry, Faculty of Education, Yokohama National University, Japan.
J Biol Chem. 1990 Sep 15;265(26):15770-5.
A new taste-modifying protein named curculin was extracted with 0.5 M NaCl from the fruits of Curculigo latifolia and purified by ammonium sulfate fractionation, CM-Sepharose ion-exchange chromatography, and gel filtration. Purified curculin thus obtained gave a single band having a Mr of 12,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence of 8 M urea. The molecular weight determined by low-angle laser light scattering was 27,800. These results suggest that native curculin is a dimer of a 12,000-Da polypeptide. The complete amino acid sequence of curculin was determined by automatic Edman degradation. Curculin consists of 114 residues. Curculin itself elicits a sweet taste. After curculin, water elicits a sweet taste, and sour substances induce a stronger sense of sweetness. No protein with both sweet-tasting and taste-modifying activities has ever been found. There are five sets of tripeptides common to miraculin (a taste-modifying protein), six sets of tripeptides common to thaumatin (a sweet protein), and two sets of tripeptides common to monellin (a sweet protein). Anti-miraculin serum was not immunologically reactive with curculin. The mechanism of the taste-modifying action of curculin is discussed.
一种名为仙茅甜蛋白的新型味觉修饰蛋白，是用0.5M氯化钠从宽叶仙茅果实中提取的，并通过硫酸铵分级分离、CM - 琼脂糖离子交换色谱和凝胶过滤进行纯化。如此获得的纯化仙茅甜蛋白在8M尿素存在下进行十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳时，呈现出一条Mr为12,000的单带。通过低角度激光光散射测定的分子量为27,800。这些结果表明天然仙茅甜蛋白是一种12,000道尔顿多肽的二聚体。仙茅甜蛋白的完整氨基酸序列通过自动埃德曼降解法确定。仙茅甜蛋白由114个残基组成。仙茅甜蛋白本身会引发甜味。在接触仙茅甜蛋白后，水会引发甜味，而酸味物质会诱导出更强的甜味感。从未发现过具有甜味和味觉修饰活性的蛋白质。与奇异果甜蛋白（一种味觉修饰蛋白）有五组共同的三肽，与索马甜蛋白（一种甜味蛋白）有六组共同的三肽，与莫内林（一种甜味蛋白）有两组共同的三肽。抗奇异果甜蛋白血清与仙茅甜蛋白没有免疫反应。文中还讨论了仙茅甜蛋白味觉修饰作用的机制。
