Homogentisic acid

Homogentisic acid (also known as melanic acid) is a phenolic acid that is an intermediate in the metabolism of tyrosine and phenylalanine. It is the metabolic precursor to benzoquinones in the biosynthesis of ubiquinone. Homogentisic acid is also the precursor of the pigment melanin in the human body.

Biochemistry

Homogentisic acid is produced from 4-hydroxyphenylpyruvate by the enzyme 4-hydroxyphenylpyruvate dioxygenase. It is then converted into maleylacetoacetic acid by the enzyme homogentisate 1,2-dioxygenase.

Clinical significance

In humans, a deficiency of the enzyme homogentisate 1,2-dioxygenase can lead to the accumulation of homogentisic acid in the body, a condition known as alkaptonuria. This can result in darkening of the urine and ochronosis, a form of arthritis characterized by pigmentation of the cartilage.

See also

• Phenylketonuria
• Tyrosinemia
• Alkaptonuria

References

Homogentisic acid Resources
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