An antioxidative mechanism mediated by the yeast N-acetyltransferase Mpr1: Oxidative stress-induced arginine synthesis and its physiological role

Saccharomyces cerevisiae Σ1278b has the MPR1 gene encoding the N-acetyltransferase Mpr1 that acetylates the proline metabolism intermediate Δ¹-pyrroline-5-carboxylate (P5C)glutamate-γ-semialdehyde (GSA) in vitro. In addition, Mpr1 protects cells from various oxidative stresses by regulating the levels of intracellular reactive oxygen species (ROS). However, the relationship between P5CGSA acetylation and antioxidative mechanism involving Mpr1 remains unclear. Here, we report the synthesis of oxidative stress-induced arginine via P5CGSA acetylation catalyzed by Mpr1. Gene disruption analysis revealed that Mpr1 converts P5CGSA into N-acetyl-GSA for arginine synthesis in the mitochondria, indicating that Mpr1 mediates the proline and arginine metabolic pathways. More importantly, Mpr1 regulate ROS generation by acetylating toxic P5CGSA. Under oxidative stress conditions, the transcription of PUT1 encoding the proline oxidase Put1 and MPR1 was strongly induced, and consequently, the arginine content was significantly increased. We also found that two deletion mutants (Δmpr12 and Δput1) were more sensitive to high-temperature stress than the wild-type strain, but that direct treatment with arginine restored the cell viability of these mutants. These results suggest that Mpr1-dependent arginine synthesis confers stress tolerance. We propose an antioxidative mechanism that is involved in stress-induced arginine synthesis requiring Mpr1 and Put1.