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Peptidase family M13 includes neprilysin and endothelin-converting enzyme I The M13 family of metallopeptidases includes neprilysin (neutral endopeptidase, NEP, enkephalinase, CD10, CALLA, EC 3.4.24.11), endothelin-converting enzyme I (ECE-1, EC 3.4.24.71), erythrocyte surface antigen KELL (ECE-3), phosphate-regulating gene on the X chromosome (PHEX), soluble secreted endopeptidase (SEP), and damage-induced neuronal endopeptidase (DINE)/X-converting enzyme (XCE). Proteins in this family fulfill a broad range of physiological roles due to the greater variation in the active site's S2' subsite allowing substrate specificity. NEP is expressed in a variety of tissues including kidney and brain, and is involved in many physiological and pathological processes, including blood pressure and inflammatory response. It degrades a wide array of substrates such as substance P, enkephalins, cholecystokinin, neurotensin and somatostatin. It is an important enzyme in the regulation of amyloid-beta (Abeta) protein that forms amyloid plaques that are associated with Alzeimers disease (AD). ECE-1 catalyzes the final rate-limiting step in the biosynthesis of endothelins via post-translational conversion of the biologically inactive big endothelins. Like NEP, it also hydrolyzes bradykinin, substance P, neurotensin, and Abeta. Endothelin-1 overproduction has been implicated in various diseases including stroke, asthma, hypertension, and cardiac and renal failure. Kell is a homolog of NEP and constitutes a major antigen on human erythrocytes; it preferentially cleaves big endothelin-3 to produce bioactive endothelin-3, but is also known to cleave substance P and neurokinin A. PHEX forms a complex interaction with fibroblast growth factor 23 (FGF23) and matrix extracellular phosphoglycoprotein, causing bone mineralization. A loss-of-function mutation in PHEX disrupts this interaction leading to hypophosphatemic rickets; X-linked hypophosphatemic (XLH) rickets is the most common form of metabolic rickets. ECEL1 is a brain metalloprotease which plays a critical role in the nervous regulation of the respiratory system, while DINE is abundantly expressed in the hypothalamus and its expression responds to nerve injury. A majority of these M13 proteases are prime therapeutic targets for selective inhibition. |
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