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.

蛋白内含是一个蛋白中的多序列，可自身从蛋白中断裂，使两侧的蛋白外显连接成成熟的蛋白。