The Fumarylacetoacetate Hydrolase (FAH) gene is located on chromosome 15q25.1. It encodes a protein of 419 amino acids, and weighs about 46 kDa. Fumarylacetoacetate hydrolase is the last enzyme in the tyrosine catabolism pathway. It converts a tyrosine byproduct called fumarylacetoacetate into smaller molecules that are either excreted by the kidneys or used in reactions that produce energy. Fumarylacetoacetate hydrolase is found in large amounts in the liver and kidneys, and smaller amounts are found in many tissues throughout the body.
Defects of the fumarylacetoacetate hydrolase enzyme are the cause of tyrosinemia; a metabolic disease characterized by elevations of tyrosine in the blood and urine, and hepatorenal manifestations. Some of the most common symptoms of this disease include hepatic necrosis, renal tubular injury, episodic weakness, self-mutilation, and seizures.