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RNPEP
RNPEP Full Name
arginyl aminopeptidase (aminopeptidase B)
RNPEP Introduction
RNPEP encodes aminopeptidase B, a zinc-dependent metallopeptidase of the M1 family that removes N-terminal basic residues, specifically arginine and lysine, from peptide substrates. First characterized in rat tissues and later cloned from liver and testis, RNPEP belongs to a conserved family of aminopeptidases that also includes aminopeptidase N, A, and the insulin-regulated aminopeptidase, all sharing a gluzincin fold anchored by the conserved HEXXH motif. The active enzyme is a monomer that binds a single catalytic zinc ion and displays a strong preference for oligopeptides such as Arg-Leu-enkephalin, Arg-Met-enkephalin, and Arg-Lys-somatostatin, provided the following position is not proline. Consistent with its conserved catalytic architecture, mutagenesis studies have shown that residues such as Asp405 and conserved tyrosines shape the substrate pocket, fine-tuning the enzyme's selectivity for basic side chains. RNPEP is widely expressed across tissues, with particularly high levels in the duodenum and colon, and it localizes to the cytosol and to extracellular vesicles, positioning it to act on both intracellular and secreted peptide pools.
Functionally, RNPEP contributes to the catabolism of bioactive peptides, including components of the renin-angiotensin system, and it can convert leukotriene A4 to leukotriene B4, linking it to inflammatory mediator metabolism. Its enzymatic activity has been associated with blood-pressure regulation, as aminopeptidase B inhibitors attenuate hypertension in rat models, and with neurological and psychiatric phenotypes, where altered plasma aminopeptidase activity has been explored as a prognostic indicator in first-episode psychosis. More recently, RNPEP has surfaced in cancer biology: tumor-derived exosomal RNPEP has been reported to promote lung metastasis of liver cancer by activating cancer-associated fibroblasts, and cytosolic aminopeptidases including RNPEP have been studied as potential colorectal-cancer markers. These diverse associations underscore how a simple exopeptidase can influence peptide signaling across cardiovascular, neural, and oncological contexts. Because RNPEP modulates the half-life of peptide hormones and neuropeptides, its activity represents a tunable checkpoint in peptide signaling, and quantifying aminopeptidase output is being explored as a non-invasive readout of metabolic and neuropsychiatric states.
Alternate Names for RNPEP
RNPEP; arginyl aminopeptidase (aminopeptidase B); aminopeptidase B; AP-B; arginine aminopeptidase; DKFZp547H084;
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