Metalloproteinases are a group of at least 25 Zn2 + -dependent exopeptidases , whose primary function is to modulate the extracellular environment by proteolysis of the protein components of extracellular matrix , membrane receptors and cytokines . These enzymes are synthesized as precursor cells and released into the extracellular space where they are activated by proteolytic cleavage of the propeptide region . Metalloproteinases are tightly regulated at the level of transcription and translation, and by specific tissue inhibitors ( tissue inhibitors of metalloproteinases , TIMPs ) .