Intein is an intervening polypeptide which can catalytic self-cleavage from a pre-protein accompanied by the concomitant joining of the two flanking polypeptides (the extein) through a peptide bond.

蛋白质内含是一个蛋白质前体中的多序列，可以催化蛋白质前体中断裂，两侧的蛋白质外显成成熟的蛋白质。