As shown in Fig. 2, different mechanisms of inhibition were found: while KELLG is a competitive inhibitor (Ki = 84 μM), KEILG acts through an uncompetitive mechanism (Ki = 16 μM). In addition, assays with an EP24.15 homologue, neurolysin (EC 3.4.24.16; EP24.16) were made, however, unexpectedly, this peptidase was not blocked by any of the two peptides (data not shown).