SCPEP1 (serine carboxypeptidase 1) is a lysosomal serine protease with broad tissue distribution, including vascular, cardiac, and pulmonary tissues 1. Its primary function involves degradation of vasoactive peptides, particularly endothelin-1 (ET-1), where it acts redundantly with cathepsin A to regulate vascular tone and blood pressure 2. SCPEP1 requires proteolytic cleavage to its mature ~35-kDa form for enzymatic activity 1. Mechanistically, SCPEP1 localizes to lysosomes and can be secreted from endothelial cells 31. In cardiac pathology, SCPEP1 exacerbates myocardial infarction-induced dysfunction by binding to Pex3 and promoting its degradation, leading to mitochondrial fission and cardiomyocyte apoptosis 4. In pulmonary fibrosis, SCPEP1 is upregulated in basal cells and serves as a robust oxidative stress biomarker (AUC 0.857) involved in pro-fibrotic signaling 5. Clinically, SCPEP1 levels are elevated in myocardial infarction and ischemic cardiomyopathy patients 4. Genetic deficiency of both SCPEP1 and cathepsin A causes hypertension and corneal dystrophy through ET-1 accumulation 6. SCPEP1 inhibition represents a potential therapeutic target for attenuating myocardial infarction 4, though its role in idiopathic pulmonary fibrosis requires further functional validation 5.