Prolyl carboxypeptidase (PRCP, EC 3.4.16.2), a lysosomal carboxypeptidase, is of interest in metabolic disorders due to its role in the C-terminal cleavage of α-melanocyte stimulating hormone (MSH) 1–13 and (pyr)-apelin-13 [1,2,3]. The gene discussed is APLN; the disease is metabolic disease.