Homogentisic

Part of speech: adjective

Definitions

1. Relating to a specific organic acid that accumulates in the body when a metabolic enzyme is missing, causing the condition alkaptonuria
2. Describing a chemical compound, a dihydroxyphenylacetic acid, produced during the breakdown of tyrosine and phenylalanine in the human body
3. Of or concerning an acid whose buildup in tissues characterizes the inherited disorder known as alkaptonuria and darkens urine on exposure to air

Etymology: Homogentisic acid is a real chemical compound, and its name is a blend of older terms. "Homo-" comes from Greek "homos," meaning "same," and "gentisic" refers to gentisic acid, itself named after the plant genus "Gentiana," the gentians, from which the acid was first isolated. The "-ic" marks it as an acid. The name records a chemical fact. Gentisic acid has a hydroxyl group arranged on its ring so that a related acid, with an extra group added, has two structurally similar ring positions. Chemists named the compound to show this "same" structural pattern, so the word describes its molecular makeup rather than any biological role. The compound matters in medicine because the body breaks down the amino acids phenylalanine and tyrosine through a pathway that produces it. When an enzyme in that pathway is missing, homogentisic acid builds up, which is the cause of alkaptonuria, a rare inherited disorder.