Homogentisic acid

C. Excreted in the urine in the rare hereditary disease alkaptonuria. Homogentisic acid is easily oxidized in the air to dark-coloured polymeric products, so that urine from patients with alkaptonuria turns gradually black. It is formed from tyrosine and is an intermediate in tyrosine breakdown in the body. Alkaptonuria is due to the absence of the liver enzyme which cleaves the aromatic ring. [Pg.205]

Self-Test 10.10B The pH of a 0.50 m aqueous solution of the metabolic intermediate homogentisic acid is 2.35. What is the K, of homogentisic acid, C7Hs(OH)2COOH ... [Pg.538]

Heterocyclics 252, 260, 299,416 n-Hexadecanol esters 63 Hexaporphyrin 102 Hexitols 426 Hexobarbital 254,255 Hexoses 161,202 Hexuronic acid 158 Histamine 294,296, 355 Homogentisic acid 166,167 Horizontal chamber 127 Hotplates 93 ff -, temperature distribution 95 Hydrazines 269,284 Hydrazone formation 71 ff -with 2,4-dinitrophenylhydrazine 71, 72, 274... [Pg.236]

Denoya CD, DD Skinner, MR Morgenstern (1994) A Streptomyces avermitilis gene encoding a 4-hydroxy-phenylpyruvic acid dioxygenase-like protein that directs the production of homogentisic acid and an ochronotic pigment in Escherichia coli. J Bacterial 176 5312-5319. [Pg.137]

Homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA) +0.45 glassy carbon t... [Pg.67]

One of the classical studies made by Garrod was of alcaptonuria. Here the abnormality, in which the urine turns black soon after voiding, although disconcerting, has only slight effects on the patient. The compound responsible is homogentisic acid. Phenylalanine, tyrosine,... [Pg.43]

Brushtail possum Tridwsurus vulpecula Sternal gland Eucalyptus leaves 5-Methyl-2-furoic acid, homogentisic acid... [Pg.51]

Homogentisate oxidase catalyzes an important reaction In tyrosine metabolism, which converts the substrate homogentisic acid to the product maleylacetoacetic acid. [Pg.24]

Homogentisic acid is excreted in urine, which darkens when left standing exposed to oxygen. [Pg.24]

Dihydroxyphenylacetic acid (homogentisic acid) [451-13-8] M 168.2, m 152 . Crystd from EtOH/CHCb. [Pg.185]

Correct answer = B. Alkaptonuria is a rare metabolic disease involving a deficiency in homogentisic acid oxidase, and the subsequent accumulation of homogentisic acid in the urine, which turns dark upon standing. The elevation of methylmalonate (due to methylmalonyl CoA mutase deficiency), phenylpyruvate (due to phenylalanine hydroxlyase deficiency), a-ketoisovalerate (due to branched-chain a-ketoacid dehydrogenase deficiency), and homocystine (due to cystathionine synthase deficiency) are inconsistent with a healthy child with darkening of the urine. [Pg.274]

For example, alkaponuria is characterized by homogentisic acid in urine phenylketonuria, which results in mental retardation, is characterized by quantities of phenylpyruvic acid in the urine. It is diagnosed in a suspected patient by determining the amount of this acid in the urine and the increased levels of phenylalanine in the plasma. Maple sugar disease is diagnosed the presence of large amounts of the branched chain amino acids, such as valine, leucine, and isoleucine in the blood and urine. [Pg.534]

The fundamental role of ascorbic acid in metabolic processes is not well understood. There is some evidence that it may be involved in metabolic hydroxylation reactions of tyrosine, proline, and some steroid hormones, and in the cleavage-oxidation of homogentisic acid. Its function in these metabolic processes appears to be related to the ability of vitamin C to act as a reducing agent. [Pg.376]

Tyrosine Alkaptonuria Homogentisic acid in urine darkens on standing in adult years, pigment deposits cause darkening of skin, cartilage arthritis develops Homogentisic acid oxidase... [Pg.525]

For instance, a 2,4-dichlorophenoxyacetic acid systemic herbicide has been determined by adopting this procedure. 2,4-Dichlorophenol and 2,5-dihydroxyphe-nylacetic acid (also known as homogentisic acid) were used as electroactive competitors and DPV for signal transduction [6]. Likewise, 2-chloro-4-hydroxy-phenoxyacetic acid was applied as the electroactive competitor for detection of the... [Pg.257]

The allyl group in the allylphenols can be oxidized, after protecting the hydroxyl group, to yield substituted phenylacetaldehydes 78 - 76 76 and phenylacetic acids. Thus, homogentisic acid LXIII is prepared readily by ozonizing the dibenzoate of allylhydroqumone LXIV, which is obtained by rearrangement of the allyl ether of hydroquinone mono-... [Pg.18]

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