A dipeptidyl peptidase (DPP) from goat brain has been purified. The purified enzyme showed a single band on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). It is a monomer with molecular weight of 69 kDa with a pI of 4.5. The K. was estimated to be 39 mu M for Arg-Arg-4-methoxy-beta-naphthylamide (Arg-Arg-4m beta NA). This enzyme is strongly inhibited by commonly used metallochelators and sulfhydryl reagents. Among various beta-naphthylamides examined, Arg-Arg-4m beta NA was the most rapidly hydrolyzed substrate. Although, initially it was thought to be the DPP-III but on the basis of its molecular weight and inhibition studies, it was concluded that this enzyme is a functional homologue of DPP-III. (c) 2006 Elsevier Inc. All rights reserved.