The transaminase-omega-amidase pathway is a redox switch in glutamine metabolism that generates alpha-ketoglutarate

Abstract

Oxidative stress is caused by short-lived molecules and metabolic changes belong to the fastest cellular responses. Here we studied how the endothelial cell metabolome reacts to acute oxidative challenges (menadione or H2O2) to identify redox-sensitive metabolic enzymes. H2O2 selectively increased alpha-ketoglutaramate (alphaKGM), a largely uncharacterized metabolite produced by glutamine transamination and a yet unrecognized intermediate of endothelial glutamine catabolism. The enzyme nitrilase-like 2 omega-amidase (NIT2) converts alphaKGM to alpha-ketoglutarate (alphaKG). Reversible oxidation of specific cysteine in NIT2 by H2O2 inhibited its catalytic activity. Furthermore, a variant in the NIT2 gene that decreases its expression is associated with high plasma alphaKGM level in humans. Endothelial-specific knockout mice of NIT2 exhibited increased levels of alphaKGM and impaired angiogenesis. Knockout of NIT2 impaired endothelial cell proliferation and sprouting and induced senescence. In conclusion, we show that the glutamine transaminase-omega-amidase pathway is a metabolic switch in which NIT2 is the redox-sensitive enzyme. The pathway is modulated in humans and functionally important for endothelial glutamine metabolism.