The importance of the three endopeptidases contributing to the formation of AA-N was metallo-, cysteine, and serine peptidase in turn.
金属蛋白酶、半胱氨酸蛋白酶在游离氨基酸的形成过程中起主要作用，丝氨酸蛋白酶次之；
2
The matrix metalloproteinases are a family of structurally related endopeptidases, they have the ability to degrade all components of extracellular matrix.