Fumarylacetoacetate hydrolase catalyzes the final step in the degradation of tyrosine - fumarylacetoacetate to fumarate, acetoacetate and succinate. Fumarylacetoacetate accumulates in hepatocytes and proximal renal tubal cells and causes oxidative damage and DNA damage leading to cell death and dysfunctional gene expression which alters metabolic processes like protein synthesis and gluconeogenesis. The increase in fumarylacetoacetate inhibits previous steps in tyrosine degradation leading to an accumulation of tyrosine in the body.