CNDP1 encodes serum carnosinase, a metallodipeptidase that catalyzes hydrolysis of Xaa-His dipeptides, with highest activity toward carnosine (β-alanyl-L-histidine) and anserine 1. The enzyme is primarily localized to the cytosol and serum 2. CNDP1 function is critical in carnosine metabolism, and genetic variants in the CNDP1 gene—particularly a 5-leucine repeat polymorphism (D18S880)—influence carnosinase activity and plasma carnosine levels 3. Reduced carnosinase activity allows carnosine accumulation, which provides cytoprotection through antioxidant, anti-inflammatory, anti-glycation, and reactive oxygen species scavenging properties 1. CNDP1 polymorphisms are associated with diabetic nephropathy susceptibility in type 2 diabetes patients, with homozygosity for the 5-leucine variant reducing nephropathy risk 4. However, the 5-leucine genotype shows sex-specific effects on cardiovascular mortality, conferring increased risk in women but not men 5. CNDP1 variants do not significantly influence longevity or coronary heart disease incidence in the general population 2. Rare loss-of-function CNDP1 variants cause carnosinaemia, an autosomal recessive trait of uncertain clinical significance 2. Lower serum CNDP1 concentrations correlate with impaired renal function in diabetic patients 3, highlighting its role in kidney disease pathogenesis.