Beta-Ala-His dipeptidase (EC 3.4.13.20, serum carnosinase) is an enzyme. This enzyme catalyses the following chemical reaction Beta-Ala-His dipeptidase (EC 3.4.13.20, serum carnosinase) is an enzyme. This enzyme catalyses the following chemical reaction This enzyme is present in the serum of humans and higher primates.