Chagolla-Lopez A, Blanco-Labra A, Patthy A, Sánchez R, Pongor S
International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
J Biol Chem. 1994 Sep 23;269(38):23675-80.
The major alpha-amylase inhibitor (AAI) present in the seeds of Amaranthus hypocondriacus, a variety of the Mexican crop plant amaranth, is a 32-residue-long polypeptide with three disulfide bridges. Purified AAI strongly inhibits the alpha-amylase activity of insect larvae (Tribolium castaneum and Prostephanus truncatus) and does not inhibit proteases and mammalian alpha-amylases. AAI was sequenced with the automated Edman method, and the disulfide bridges were localized using enzymatic and chemical fragmentation methods combined with N-terminal sequencing. AAI is the shortest alpha-amylase inhibitor described so far which has no known close homologs in the sequence data bases. Its residue conservation patterns and disulfide connectivity are related to the squash family of proteinase inhibitors, to the cellulose binding domain of cellobiohydrolase, and to omega-conotoxin, i.e. a group of small proteins termed "knottins" by Nguyen, D. L., Heitz, A., Chiche, L., Castro, B., Boigegrain, R., Favel, A., and Coletti-Previero, M. ((1990) (Biochimie 72, 431-435) The three-dimensional model of AAI was built according to the common structural features of this group of proteins using side-chain replacement and molecular dynamics refinement techniques.
存在于墨西哥农作物苋属植物低地苋种子中的主要α-淀粉酶抑制剂（AAI）是一种由32个氨基酸残基组成的多肽，含有三个二硫键。纯化后的AAI能强烈抑制昆虫幼虫（赤拟谷盗和米象）的α-淀粉酶活性，而不抑制蛋白酶和哺乳动物的α-淀粉酶。采用自动Edman法对AAI进行测序，并结合N端测序，利用酶切和化学裂解方法确定二硫键的位置。AAI是迄今为止所描述的最短的α-淀粉酶抑制剂，在序列数据库中没有已知的近亲同源物。其残基保守模式和二硫键连接与蛋白酶抑制剂的南瓜家族、纤维二糖水解酶的纤维素结合结构域以及ω-芋螺毒素有关，即Nguyen, D. L., Heitz, A., Chiche, L., Castro, B., Boigegrain, R., Favel, A., 和Coletti-Previero, M.（（1990）（《生物化学》72, 431 - 435））所定义的一组被称为“扭结蛋白”的小蛋白。根据该组蛋白的共同结构特征，利用侧链置换和分子动力学优化技术构建了AAI的三维模型。
