Structural insights into human Arginase-1 pH dependence and its inhibition by the small molecule inhibitor CB-1158.

•Side-by-side biochemical comparison of the inhibitors ABH, nor-NOHA and CB-1158.•Arginase-1 binding, inhibition and stabilization by ABH and CB-1158 is pH-dependent.•ABH and CB-1158 have slow association kinetics and a long target residence time.•At higher pH, the catalytic center adopts a more symmetrical coordination structure.•CB-1158 forms an additional hydrogen-bond network in the active site compared to ABH.