Rehfeld J F, Hansen C P, Johnsen A H
Department of Clinical Biochemistry, University of Copenhagen, Denmark.
EMBO J. 1995 Jan 16;14(2):389-96. doi: 10.1002/j.1460-2075.1995.tb07013.x.
Expression of bioactive peptides requires several modifications of the primary translation product. Gastrin, a vertebrate gut hormone, occurs in multiple forms, including a bioactive fragment of the predominant gastrin-17. Gastrin-17 is, however, without known cleavage sites. In order to identify the new site, we therefore isolated, from antral mucosa, fragments of gastrin-34 and -17 monitored by monospecific immunoassays. After three steps of reverse-phase chromatography, the short gastrins were identified as hepta-, hexa- and pentapeptide amides. By far the most abundant of these was tyrosine O-sulfated gastrin-6. The near complete sulfation contrasts with the larger gastrins, of which only half are sulfated. The longest N-terminal fragment of gastrin-34 was a hexadecapeptide without complementarity to the short gastrins. Instead, the predominant N-terminal fragment of gastrin-17 was the decapeptide complementary to gastrin-7. Therefore the novel processing site is the Glu10-Ala11 bond that follows a poly(Glu6-10) sequence. Moreover, gastrin-7 is apparently trimmed, with subsequent accumulation of sulfated gastrin-6. Consequently, O-sulfated tyrosine ensures production of a new hormone which stimulates gastric acid secretion as potently as gastrin-17.
生物活性肽的表达需要对初级翻译产物进行多种修饰。胃泌素是一种脊椎动物肠道激素，有多种形式，包括主要的胃泌素-17的生物活性片段。然而，胃泌素-17没有已知的切割位点。为了确定新的位点，我们因此从胃窦黏膜中分离出胃泌素-34和-17的片段，并通过单特异性免疫测定进行监测。经过三步反相色谱法后，短胃泌素被鉴定为七肽、六肽和五肽酰胺。其中最丰富的是酪氨酸O-硫酸化胃泌素-6。这种几乎完全硫酸化与较大的胃泌素形成对比，较大的胃泌素只有一半被硫酸化。胃泌素-34最长的N端片段是一个十六肽，与短胃泌素没有互补性。相反，胃泌素-17的主要N端片段是与胃泌素-7互补的十肽。因此，新的加工位点是Glu10-Ala11键，它位于聚（Glu6-10）序列之后。此外，胃泌素-7显然被修剪，随后硫酸化胃泌素-6积累。因此，O-硫酸化酪氨酸确保产生一种新的激素，其刺激胃酸分泌的效力与胃泌素-17相同。
