In human macrophages, a dipeptidase (DPEP) is proposed to hydrolyse maresin conjugates in tissue regeneration 2 (MCTR2) to MCTR3, identified as 13(R)-cysteinyl, 14(S)-hydroxy-4Z,7Z,9E,11E,13R,14S,16Z,19Zdocosahexaenoic acid (Dalli et al. 2014, 2016a, 2016b). Incubation of human macrophages with MCTR2 and a DPEP inhibitor demonstrates significantly higher MCTR2 levels and significantly lower MCTR3 levels, suggesting a DPEP mediates MCTR2 hydrolysis (Dalli et al. 2016a). MCTR3 displays potent activity in proresolution of inflammation and tissue regeneration (Dalli et al. 2016b).