Homogentisate, also known as homogentisic acid, is an aromatic organic compound that is used in many biochemical pathways. It is a component of the naturally occurring pigment melanin, the pigment responsible for the color of skin, hair, and eyes. It is also responsible for the production of tyrosine, which is essential for the formation of proteins. Homogentisate is found in many foods, including apples, grapes, oranges, tomatoes, and plums.
Homogentisate is an important intermediate in the pathway of the metabolism of the amino acid phenylalanine. The enzyme phenylalanine hydroxylase catalyzes the conversion of phenylalanine to homogentisate, which is then further broken down by homogentisate oxidase to form maleylacetoacetate. Maleylacetoacetate, in turn, is further metabolized to fumarate and acetoacetate.
The accumulation of homogentisate in the body can lead to the condition known as alkaptonuria, which is characterized by the darkening of the urine. Homogentisate is also thought to be a factor in the formation of skin and joint conditions, such as osteoarthritis.
In addition to its role in human physiology, homogentisate is also used in the production of dyes, perfumes, and pharmaceuticals. It is also used as a food preservative and as a precursor to the production of compounds such as pyrrole and indigo.