What does homogentisic acid oxidase do?
Homogentisate oxidase is responsible for a specific step in the breakdown of phenylalanine and tyrosine. Previous steps convert the two amino acids into a molecule called homogentisic acid. Homogentisate oxidase adds two oxygen atoms to homogentisic acid, converting it to another molecule called maleylacetoacetate.
What condition is developed in the absence of homogentisic acid oxidase?
Alcaptonuria (Ochronosis) Ochronosis is a hereditary metabolic abnormality arising from the absence of homogentisic acid oxidase and consequent accumulation of homogentisic acid in various organs, including connective tissues.
What does homogentisic acid mean?
noun. an intermediate compound in the metabolism of tyrosine and of phenylalanine, found in excess in the blood and urine of persons affected with alkaptonuria.
How is homogentisic acid formed in the body?
It is an intermediate in the catabolism of aromatic amino acids such as phenylalanine and tyrosine. 4-Hydroxyphenylpyruvate (produced by transamination of tyrosine) is acted upon by the enzyme 4-hydroxyphenylpyruvate dioxygenase to yield homogentisate.
What causes homogentisic acid?
A defect in the HGD gene causes alkaptonuria. The gene defect makes the body unable to properly break down certain amino acids (tyrosine and phenylalanine). As a result, a substance called homogentisic acid builds up in the skin and other body tissues. The acid leaves the body through the urine.
How is homogentisic acid formed?
Homogentisic acid, also known as melanic acid, is an intermediate in the breakdown or catabolism of tyrosine and phenylalanine. It is generated from the compound p-hydroxyphenylpyruvate through the enzyme p-hydroxyphenylpyruvate dehydrogenase.
What are Alkaptone bodies?
Alkaptonuria, or “black urine disease”, is a very rare inherited disorder that prevents the body fully breaking down two protein building blocks (amino acids) called tyrosine and phenylalanine. It results in a build-up of a chemical called homogentisic acid in the body.
Is homogentisic acid present in the urine of healthy people?
…in an abnormal accumulation of homogentisic acid, a normal intermediate in the metabolism of the amino acid tyrosine. Some homogentisic acid is excreted in the urine, to which, upon alkalinization and oxidation, it imparts a black colour.
Which amino acids are precursors of homogentisic acid?
4-Hydroxyphenylpyruvate hydroxylase is a key enzyme in the metabolism of the amino acid tyrosine. It is an Fe-dependent dioxygenase which converts tyrosine to homogentisate. In plants homogentisate is a metabolic precursor to the plant specific redox co-factors plastoquinone and tocopherol (vitamin E).