How does phenylacetate, the active metabolite of glycerol phenylbutyrate, promote nitrogen excretion?

Phenylacetate, the active metabolite of glycerol phenylbutyrate, conjugates with glutamine via acetylation in the liver and kidneys to form PAGN, which is excreted by the kidneys and, like urea, carries two moles of nitrogen per mole, providing an alternative route for waste nitrogen excretion.