酶催化合成CCK-4三肽片段(英文)

Enzymatic synthesis of CCK-4 tripeptide fragment

目的探讨酶法合成胃泌激素CCK-4 C-末端片段三肽衍生物Phac-Met-Asp(OMe)-Phe-NH2.方法以Phac-Met-OCam为起始原料,采用三种蛋白酶,即α-糜蛋白酶、木瓜蛋白酶、嗜热菌蛋白酶(α-chymotrypsin,papain,thermolysin),经过三步酶促反应得到目标三肽化合物;研究了酶催化条件下Met-Asp肽键的形成以及天门冬氨酸双酯中α-酯的酶催化条件下的选择性水解;对酶以及反应介质的选择等酶促合成条件进行了研究.结果三步酶促反应均可得到较合适的收率(63%～92%),产物经FAB-MS、FD-MS质谱确认.结论以α-糜蛋白酶为酶催化剂,在含有1.5%0.05 mol/LT^s-HCl缓冲液的乙酸乙酯介质中,Phac-Met-OCam和H-Asp(OMe)2缩合可得到收率大于63%的缩合产物;木瓜蛋白酶催化下可选择性水解Phac-Met-Asp(OMe)2中的α-酯而保留β-酯;嗜热菌蛋白酶能有效地催化Phac-Met-Asp(OMe)-OH与H-Phe-NH2生成肽键.

Objective To synthesize a tripeptide derivative Phac-Met-Asp(OMe)-Phe -NH 2 , which is a fragment of the gastrin C-terminal tetrapeptide CCK-4, by enzymatic reaction. Methods Three free enzymes, α-chymotrypsin, papain and thermolysin from acyl donor Phac-Met-OCam was involved in three steps. The choice of appropriate enzymes and solvents was selected. Results All enzymatic reactions were obtained in reasonable yields(63%-92%). FAB-MS and FD-MS verified the correct molecular mass of the peptides. Conclusion Studies on the α-chymotrypsin catalyzed coupling reaction between Phac-Met-OCam and H-Asp(OMe) 2 have focused on the low water content media. By papain catalyzed saponification of Phac-Met-Asp(OMe) 2 , α-methyl ester of aspartic acid is selectively hydrolyzed to retain β-methyl ester, and Phac-Met-Asp(OMe)-OH and H-Phe-NH 2 can be coupled efficiently by thermolysin.