4-Hydroxyphenylpyruvate dioxygenase

4-Hydroxyphenylpyruvate dioxygenase

Ribbon diagram of 4-Hydroxyphenylpyruvate dioxygenase

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is an enzyme that plays a crucial role in the catabolism of the amino acid tyrosine. It catalyzes the conversion of 4-hydroxyphenylpyruvate to homogentisate, a key step in the metabolic pathway.

Function

4-Hydroxyphenylpyruvate dioxygenase is involved in the tyrosine catabolism pathway. It catalyzes the reaction that converts 4-hydroxyphenylpyruvate into homogentisate. This reaction is an essential step in the breakdown of tyrosine, leading to the production of acetoacetate and fumarate, which are further processed in the citric acid cycle.

Mechanism

Reaction catalyzed by 4-Hydroxyphenylpyruvate dioxygenase

The enzyme utilizes molecular oxygen to catalyze the oxidative decarboxylation of 4-hydroxyphenylpyruvate. The reaction involves the incorporation of both atoms of molecular oxygen into the substrate, resulting in the formation of homogentisate and carbon dioxide.

Structure

4-Hydroxyphenylpyruvate dioxygenase is a mononuclear non-heme iron enzyme. The active site contains an iron ion that is essential for its catalytic activity. The enzyme's structure allows it to bind to its substrate and facilitate the reaction through a series of coordinated steps involving the iron center.

Clinical significance

Inhibition of 4-hydroxyphenylpyruvate dioxygenase is a target for certain herbicides and drugs. For example, the inhibition of this enzyme can lead to the accumulation of toxic intermediates in plants, making it an effective target for herbicidal action. In humans, mutations in the gene encoding this enzyme can lead to metabolic disorders such as tyrosinemia type III.

Related pages

• Tyrosine catabolism
• Homogentisate
• Citric acid cycle
• Tyrosinemia

Gallery

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  Proposed reaction mechanism of 4-Hydroxyphenylpyruvate dioxygenase