# The transaminase-ω-amidase pathway senses oxidative stress to control glutamine metabolism and α-ketoglutarate levels in endothelial cells

## TL;DR

This study reveals how oxidative stress affects endothelial cell metabolism through a redox-sensitive enzyme called NIT2, which controls glutamine breakdown and impacts angiogenesis.

## Contribution

The discovery of NIT2 as a redox-sensitive metabolic switch in glutamine catabolism in endothelial cells is novel.

## Key findings

- H2O2 increases α-ketoglutaramate (αKGM) levels by impairing NIT2 activity through cysteine oxidation.
- NIT2 depletion in endothelial cells reduces angiogenesis and proliferation while inducing senescence.
- A NIT2 gene variant is linked to higher plasma αKGM levels in humans.

## Abstract

Oxidative stress is a major driver of cardiovascular disease; however, the fast changes in cellular metabolism caused by short-lived reactive oxygen species (ROS) remain ill-defined. Here, we characterized changes in the endothelial cell metabolome in response to acute oxidative challenges and identified novel redox-sensitive metabolic enzymes. H2O2 selectively increased the amount of α-ketoglutaramate (αKGM), a largely uncharacterized metabolite produced by glutamine transamination and an unrecognized intermediate of endothelial glutamine catabolism. In addition, H2O2 impaired the catalytic activity of nitrilase-like 2 ω-amidase (NIT2), the enzyme that converts αKGM to α-ketoglutarate (αKG), by the reversible oxidation of specific cysteine residues. Moreover, a NIT2 gene variant exhibited decreased expression in humans and was associated with increased plasma αKGM concentration. Endothelial-specific knockout of NIT2 in mice increased cellular αKGM levels and impaired angiogenesis. Further, NIT2 depletion impaired endothelial cell proliferation, sprouting, and induced senescence. In conclusion, we uncover NIT2 as a redox-sensitive enzyme of the glutamine transaminase-ω-amidase pathway that acts as a metabolic switch modulating endothelial glutamine metabolism in mice and humans.

Oxidative stress is a driver of cardiovascular disease, but the redox regulation of endothelial cell metabolism remains poorly defined. This metabolome analysis uncovers the glutamine metabolism enzyme nitrilase-like 2 ω-amidase (NIT2) as a redox-sensitive non-canonical switch in endothelial cells, controlling glutamine catabolism and angiogenesis.

NIT2-mediated conversion of α-ketoglutaramate (αKGM) to α-ketoglutarate (αKG) is redox-sensitive and controls glutamine catabolism in endothelial cells.NIT2 activity is impaired by H2O2 through oxidation of cysteine residues, increasing the rate of cellular αKGM production.Depletion of NIT2 in endothelial cells decreases angiogenesis and cell proliferation, inducing senescence.

NIT2-mediated conversion of α-ketoglutaramate (αKGM) to α-ketoglutarate (αKG) is redox-sensitive and controls glutamine catabolism in endothelial cells.

NIT2 activity is impaired by H2O2 through oxidation of cysteine residues, increasing the rate of cellular αKGM production.

Depletion of NIT2 in endothelial cells decreases angiogenesis and cell proliferation, inducing senescence.

The glutamine metabolism enzyme NIT2 acts as redox-sensitive, non-canonical switch factor for endothelial cell catabolism and angiogenesis.