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4-Hydroxyphenylpyruvate dioxygenase (HPPD), also known as α-ketoisocaproate dioxygenase (KIC dioxygenase), is an Fe(II)-containing non-heme oxygenase that catalyzes the second reaction in the catabolism of tyrosine - the conversion of 4-hydroxyphenylpyruvate into homogentisate.
4-Hydroxyphenylpyruvate dioxygenase (HPPD) is an enzyme found in both plants and animals, which catalyzes the catabolism of the amino acid tyrosine. [4] Preventing the breakdown of tyrosine has three negative consequences: the excess of tyrosine stunts growth; the plant suffers oxidative damage due to lack of tocopherols (vitamin E); and ...
Several hydroxylase enzymes are believed to incorporate an NIH shift in their mechanism, including 4-hydroxyphenylpyruvate dioxygenase and the tetrahydrobiopterin dependent hydroxylases. The name NIH shift arises from the US National Institutes of Health from where studies first reported observing this transformation.
Tyrosinemia type III is a rare disorder caused by a deficiency of the enzyme 4-hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27), encoded by the gene HPD. [2] This enzyme is abundant in the liver, and smaller amounts are found in the kidneys. It is one of a series of enzymes needed to break down tyrosine.
The mechanism of action of nitisinone involves inhibition of 4-Hydroxyphenylpyruvate dioxygenase (HPPD). [5] [6] This is a treatment for patients with Tyrosinemia type 1 as it prevents the formation of 4-Maleylacetoacetic acid and fumarylacetoacetic acid, which have the potential to be converted to succinyl acetone, a toxin that damages the liver and kidneys. [4]
4-Hydroxyphenylpyruvic acid (4-HPPA) is an intermediate in the metabolism of the amino acid phenylalanine. The aromatic side chain of phenylalanine is hydroxylated by the enzyme phenylalanine hydroxylase to form tyrosine. The conversion from tyrosine to 4-HPPA is in turn catalyzed by tyrosine aminotransferase. [2]
L-tyrosine + 2-oxoglutarate 4-hydroxyphenylpyruvate + L-glutamate In humans, the tyrosine aminotransferase protein is encoded by the TAT gene . [ 7 ] A deficiency of the enzyme in humans can result in what is known as type II tyrosinemia , wherein there is an abundance of tyrosine as a result of tyrosine failing to undergo an aminotransferase ...
The positional description para, abbreviated p, mean that the hydroxyl group and side chain on the phenyl ring are across from each other (see the illustration below). The next oxidation step catalyzes by p-hydroxyphenylpyruvate dioxygenase and splitting off CO 2 homogentisate (2,5-dihydroxyphenyl-1-acetate). [25]