Homogentisic acid oxidase, also known as homogentisate 1,2-dioxygenase, is an enzyme found in plants and animals which is involved in the metabolism of the amino acid tyrosine. This enzyme catalyzes the oxidation of homogentisic acid (HGA) to maleylacetoacetate and hydrogen peroxide. In humans, mutations in this enzyme cause the condition known as alkaptonuria, an inherited metabolic disorder in which the body is unable to break down the amino acid tyrosine.
In plants, homogentisic acid oxidase is involved in the production of the pigment anthocyanin which gives many plants their distinctive colors. This enzyme acts on the precursor molecule, HGA, to produce anthocyanins which are responsible for many of the colors seen in flowers and fruits.
In addition to its role in the metabolism of tyrosine and the production of anthocyanins, homogentisic acid oxidase has also been implicated in the development of some forms of cancer. In particular, the enzyme has been shown to play a role in the formation of some types of melanoma and certain types of leukemia.
The structure of this enzyme has been studied in both its native form and in its mutant forms associated with certain forms of cancer. It has been determined that the enzyme is composed of two monomers, each containing three domains. The first domain contains the active site of the enzyme which is responsible for the oxidation of HGA. The second domain contains a catalytic site which is responsible for the production of hydrogen peroxide, while the third domain is responsible for the binding of HGA.
In summary, homogentisic acid oxidase is an enzyme found in both plants and animals which is involved in the metabolism of the amino acid tyrosine and the production of the pigment anthocyanin. In humans, mutations in this enzyme can cause alkaptonuria and it has been implicated in the development of certain forms of cancer. The enzyme is composed of two monomers, each containing three domains, and the active site of the enzyme is responsible for the oxidation of HGA.
