翻译后修饰变成活性的蛋白质或肽。一些细胞會分泌蛋白质前体。 胰岛素原(英语:Proinsulin)就是一種前肽 ,它被切去一段无活性的C肽(英语:C-peptide)之后,便成为有活性的胰岛素。 Alberts, Bruce. Molecular biology of the cell. New York:
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