Arginase: an old enzyme with new tricks

Highlights • Arginase is the enzyme that converts L-arginine to urea and L-ornithine, functions important for protection against NH3 toxicity and for cell growth and repair. • Excessive arginase activity has been linked to cardiovascular diseases because it reduces the supply of L-arginine needed by nitric oxide (NO) synthase to produce NO. • Excessive activity of the arginase/ornithine pathway can also contribute to vascular structural problems and neural toxicity. • Recent research has identified inflammatory agents and reactive oxygen species as drivers of the pathologic elevation of arginase activity and expression.