Oxidase homogentisic acid

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. 

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

Inhibition of homogentisic acid oxidase, leading to local accumulation of homogentisic acid followed by polymerization that forms the ochronotic blue-black pigment. 

CH, 1 COO Acetoacetate 0, Homogentisic acid oxidase ascorbic acid GSH... 

A. The correct response is dihydropteridine reductase. This enzyme reduces dihydrobiopterin to tetrahydrobiopterin the obligate electron donor for phenylalanine hydroxylase. Tyrosinase is the first enzyme on the pathway to melanin. Dopamine hydroxylase and tyrosine transaminase are enzymes on other tyrosine metabohc tracts. Homogentisic acid oxidase is an enzyme on the pathway of tyrosine to fumarate and acetoacetate. 

The appearance of homogentisic acid is the classic feature of alcaptonuria, which is due to a specific defect in homogentisic acid oxidase activity (L2). 

Alkaptonuria is a rare inborn error of metabolism caused by a lack of the enzyme homogentisic acid oxidase. The deficiency causes a failure to oxidize homogentisate, which is excreted in the urine in abundance. Polymerization of the metabolite, especially under alkaline conditions in the presence of oxygen, leads to the production of a black polymer. This makes the urine black if it is exposed to air for a few hours and in vivo, cartilage and other connective tissues become pigmented and take on an orange color (hence the name ochronosis for this state of the tissues the ocher color is readily seen postmortem). In later years the patients develop severe arthritis. 

A rare inborn error of metabolism in which there is a deficiency of the enzyme homogentisic acid oxidase. It is inherited as an autosomal recessive. 

The oxidative breakdown of the amino acid tyrosine contains a stage in which homogentisic acid is converted to maley-lacetoacetic acid, a reaction catalysed by homogentisic acid oxidase. A deficiency of this enzyme results in the accumulation... 

Alkaptonuria (Homogentisic aciduria) Homogentisic acid Homogentisic acid oxidase (EC 1.13.11.5) 16.5... 

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