Sandbox Reserved 322: Difference between revisions

In general arginase is known to convert L-arginine into urea and L-ornithine, via hydrolysis, the proposed mechanism is adopted from Kanyo and colleagues as shown in figure 3<ref name="d"/>. In the first step of the hydrolytic mechanism, Asp 128 stabilizes the metal-bridging hydroxide ion with a hydrogen bond during a nucleophilic attack at the guanidinium carbon of arginine<ref name="d"/>. The resulting tetrahedral intermediate fall apart once a proton is transferred to the amino group of ornithine, and the proton transfer is mediated by Asp 128<ref name="d"/>. It is proposed that His 141 shuttles a proton from bulk solvent to the ε-amino group of ornithine before production dissociation<ref name="d"/>. Before product dissociation, a water molecule displaces urea<ref name="d"/>. In addition, the metal coordination facilitates the ionization of this water molecule to regenerate a nucleophilic hydroxide ion<ref name="d"/>. Here, proton transfer to bulk solvent may again be mediated by shuttle-group His 141<ref name="d"/>.