Catalyzes the peptide bond hydrolysis in Xaa-His dipeptides, displaying the highest activity toward carnosine (beta-alanyl-L-histidine) and anserine (beta-alanyl-3-methyl-histidine). Preferential hydrolysis of the beta-Ala-|-His dipeptide (carnosine), and also anserine, Xaa-|-His dipeptides and other dipeptides including homocarnosine. carnosine + H2O = beta-alanine + L-histidine anserine + H2O = beta-alanine + N(pros)-methyl-L-histidine H2O + L-alanyl-L-histidine = L-alanine + L-histidine glycyl-L-histidine + H2O = glycine + L-histidine H2O + L-homocarnosine = 4-aminobutanoate + L-histidine Binds 2 Zn(2+) ions per subunit. Activated by cadmium ions (PubMed:12473676). Inhibited by the metal chelator 1,10-o-phenantrolin. The inhibitory concentration 50% (IC(50)) is 5 uM. 1 hour incubation in 50 mM Tris-HCl, pH 7.5. Optimum pH is 8.5. Homodimer. Found in serum and adult nervous central system. Absent in serum from patients with homocarnosinosis. The number of trinucleotide (CTG) repeat varies among different alleles leading to insertion of Leu residues in the signal peptide. The allele with 5 leucines (as shown in the reference entry) is known as the Mannheim allele. Diabetic patients with the CNDP1 Mannheim allele are less susceptible for nephropathy. Belongs to the peptidase M20A family.