Theoretical studies on the structural and magnetic property of arginase active site

Abstract

The chemical species of solvent molecule (WB) between two manganese ions in the active site of arginase is investigated based on the structural and magnetic property. The calculated magnetic coupling constant (J ab ) values at UBH&HLYP level of theory are − 1.9 cm− 1 for WB = H2O and − 5.7 cm− 1 for WB = OH− , respectively. In comparison with the experimental value (J ab = ∼ − 2.0 cm− 1), H2O is the most likely candidate to WB in the initial structure. Natural orbital analyses reveal that WB plays an important role for keeping the geometry of the Mn–O(WB)–Mn core rigid rather than mediating superexchange interaction. The result indicates that WB does not have to shift to one Mn ion as an initiation of the hydrolysis reaction.