Hilsted L, Rehfeld J F
University Department of Clinical Chemistry, Rigshospitalet, Copenhagen, Denmark.
J Biol Chem. 1987 Dec 15;262(35):16953-7.
Using radioimmunoassays for amidated and glycine-extended gastrin before and after trypsin-carboxypeptidase B cleavage and chromatography, alpha-carboxyamidation of porcine antral progastrin has been related to tyrosine-O-sulfation and proteolytic cleavages. Corresponding to the sequence at the proteolysis and amidation site, -Gly-Arg-Arg-, antrum contained three COOH-terminally extended precursor types. The glycine-extended gastrins were present in the highest concentrations (241 +/- 58 pmol/g). The degree of tyrosine-O-sulfation was identical for amidated and precursor gastrins irrespective of component size, whereas the component size differed for glycine-extended and amidated forms. For instance, gastrin-34-Gly constituted 54% of the glycine-extended gastrins, while gastrin-34 comprised 8% of the amidated gastrins. The results indicate that tyrosine-O-sulfation occurs prior to NH2-terminal cleavages, which again precede carboxyamidation; but a significant correlation between tyrosine-O-sulfation and proteolytic cleavages or alpha-carboxy-amidation of antral gastrin could not be demonstrated. Furthermore, our results suggest that the immediate precursor of the principal hormonal form, gastrin-17, is gastrin-17-Gly rather than gastrin-34 as previously believed.
运用放射免疫分析法，在胰蛋白酶 - 羧肽酶B裂解及色谱分析前后，对酰胺化和甘氨酸延伸型胃泌素进行检测，猪胃窦前胃泌素的α - 羧基酰胺化与酪氨酸 - O - 硫酸化及蛋白水解裂解相关。对应于蛋白水解和酰胺化位点的序列 - Gly - Arg - Arg -，胃窦含有三种羧基末端延伸的前体类型。甘氨酸延伸型胃泌素浓度最高（241±58 pmol/g）。无论组分大小如何，酰胺化胃泌素和前体胃泌素的酪氨酸 - O - 硫酸化程度相同，而甘氨酸延伸型和酰胺化形式的组分大小不同。例如，胃泌素 - 34 - Gly占甘氨酸延伸型胃泌素的54%，而胃泌素 - 34占酰胺化胃泌素的8%。结果表明，酪氨酸 - O - 硫酸化发生在氨基末端裂解之前，而氨基末端裂解又先于羧基酰胺化；但未证实胃窦胃泌素的酪氨酸 - O - 硫酸化与蛋白水解裂解或α - 羧基酰胺化之间存在显著相关性。此外，我们的结果表明，主要激素形式胃泌素 - 17的直接前体是胃泌素 - 17 - Gly，而非先前认为的胃泌素 - 34。
