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Fumarylacetoacetate (FAA) hydrolase family This family consists of fumarylacetoacetate (FAA) hydrolase, or fumarylacetoacetate hydrolase (FAH) and it also includes HHDD isomerase/OPET decarboxylase from E. coli strain W. FAA is the last enzyme in the tyrosine catabolic pathway, it hydrolyses fumarylacetoacetate into fumarate and acetoacetate which then join the citric acid cycle. Mutations in FAA cause type I tyrosinemia in humans this is an inherited disorder mainly affecting the liver leading to liver cirrhosis, hepatocellular carcinoma, renal tubular damages and neurologic crises amongst other symptoms. The enzymatic defect causes the toxic accumulation of phenylalanine/tyrosine catabolites. The E. coli W enzyme HHDD isomerase/OPET decarboxylase contains two copies of this domain and functions in fourth and fifth steps of the homoprotocatechuate pathway; here it decarboxylates OPET to HHDD and isomerizes this to OHED. The final products of this pathway are pyruvic acid and succinic semialdehyde. This family also includes various hydratases and 4-oxalocrotonate decarboxylases which are involved in the bacterial meta-cleavage pathways for degradation of aromatic compounds. 2-hydroxypentadienoic acid hydratase encoded by mhpD in E. coli is involved in the phenylpropionic acid pathway of E. coli and catalyzes the conversion of 2-hydroxy pentadienoate to 4-hydroxy-2-keto-pentanoate and uses a Mn2+ co-factor. OHED hydratase encoded by hpcG in E. coli is involved in the homoprotocatechuic acid (HPC) catabolism. XylI in P. putida is a 4-Oxalocrotonate decarboxylase. |
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Jiyao W et al.(2023). "The conserved domain database in 2023.",