Membrane metallo endopeptidase (MME), also known as neprilysin or common acute lymphoblastic leukemia antigen (CALLA), is a type II transmembrane metalloproteinase enzyme encoded by the MME gene. It is widely expressed in various tissues and plays a crucial role in the regulation of peptide signaling by cleaving peptide bonds within proteins.
The MME enzyme is characterized by its ability to hydrolyze a broad range of biologically active peptides, including neuropeptides, peptide hormones, and cytokines. It primarily functions at the cell surface, where it can cleave peptides either extracellularly or intracellularly, depending on the localization of the substrate. This enzymatic activity makes MME essential in numerous physiological processes, such as blood pressure regulation, immune response modulation, and the breakdown of amyloid-β peptides implicated in Alzheimer's disease.
The MME protein structure consists of an extracellular domain responsible for substrate recognition and catalysis, a transmembrane domain that anchors it to the cell membrane, and a short cytoplasmic tail involved in intracellular signaling. Its metalloproteinase activity relies on a zinc ion at the active site, which is coordinated with specific amino acid residues.
Due to its diverse substrate specificity and involvement in critical biological pathways, membrane metallo endopeptidase has become an attractive target for therapeutic interventions. Inhibitors of MME have been studied for their potential in treating diseases where excess activity of certain peptides is detrimental, such as heart failure, cancer, and neurodegenerative disorders. Additionally, the measurement of soluble neprilysin in biological fluids has been explored as a diagnostic and prognostic tool for various pathological conditions.
