RNPEPL1 (arginyl aminopeptidase like 1) is a zinc metalloaminopeptidase belonging to the M1 family of metallopeptidases that catalyzes N-terminal proteolysis with broad substrate specificity 1. The full-length enzyme preferentially hydrolyzes N-terminal methionine, citrulline, and glutamine residues 1, and exhibits notable activity against peptide substrates including met-enkephalin, kallidin, and bradykinin, with unique chain-length dependent cleavage patterns 2. RNPEPL1 shows ubiquitous tissue distribution consistent with housekeeping functions and undergoes alternative splicing generating truncated protein variants 1. Disease relevance: RNPEPL1 was identified as part of a matrix metalloproteinase-related prognostic signature in hepatocellular carcinoma (HCC), where elevated expression correlates with worse overall survival and increased drug resistance to sorafenib, cisplatin, and cytarabine 3. Additionally, RNPEPL1 functions as a competing endogenous RNA (ceRNA) regulated by LINC01260 in nonalcoholic fatty liver disease (NAFLD), where modulation of RNPEPL1 expression through the LINC01260-RXRB regulatory axis affects hepatocyte lipid accumulation and steatosis progression 4. These findings suggest RNPEPL1 plays roles in both hepatic metabolic dysfunction and cancer progression, potentially impacting therapeutic strategies in liver disease.