Figure 4: Outline of tyrosine metabolism. Fumarylacetoacetate formed in the process of tyrosine metabolism is broken down to fumarate and acetate by fumarylacetoacetate hydrolase (FAH). Acetoacetate, a ketone body, can be converted to acetyl-CoA, which in turn can enter Krebs cycle. Deficiency of FAH results in accumulation of succinyl acetone and causes the symptoms of Tyrosinaemia type 1.