Alcaptonuria is a rare, hereditary, metabolic disorder characterized by a defect in the oxidation of tyrosine (l-3). In this condition homogentisic acid, an intermediary product of tyrosine degradation in mammalian liver, is excreted in the urine. This disorder has been attributed to an abnormality of the enzyme system, homogentisic acid oxidase, but the exact nature of the abnormality has not ...

Alcaptonuria is an extremely rare metabolic disease and is defined as an autosomal recessive inherited deficiency of the hepatic enzyme oxidase of the homogentisic acid [1,2] (Figure 1). Deficiency of the enzyme causes accumulation of the homogentisic acid in the cells and the body fluids. The disease is characterized by the following three specific conditions, excretion of homogentisic acid in...

Growth of Yarrowia lipolvtica W3-180 on a poor C-source in the presence of phenylalanine or tyrosine results in the formation of homogentisic acid. Melanin is formed, if desired, by bringing the medium to pH >10 whereupon the homogentisic acid spontaneously polymerizes. Y. lipolytica YB3-180 was grown in a minimal salts medium contg. 0.5 g glucose/L and tyrosine 5 mM. After 5 days incubation (2...

Homogentisic acid, which is considered to be an intermediate in the metabolism of tyrosine and phenylalanine, is excreted in a number of different conditions. The most widely studied of these, which is caused by a genetic inability to oxidize homogentisic acid, was termed alcaptonuria, owing to the characteristic darkening of the urine on standing. It has also been shown (Sealock & Silberstein,...

Although the probability that homogentisic acid is an intermediate in the conversion of phenylalanine and tyrosine to acetoacetate is indicated by many experiments with humans (l-5), animals (6-9), and tissue preparations (lO-13), no direct evidence has been reported concerning the mechanism of its oxidation. However, the formation of /?-ketoadipic acid from phenol in the presence of cholera Vi...

All the more recent work on alkaptonuria has tended to show that the constant feature of that condition is the excretion of homogentisic acid, to the presence of which substance the special properties of alkapton urine, the darkening with alkalies and on exposure to air, the power of staining fabrics deeply, and that of reducing metallic salts, are alike due. In every case which has been fully ...

normally retained in the body because of its high renal clearance; the absence of the HGD enzyme leads to abundant urinary excretion of homogentisic acid, which darkens slowly upon oxidation by prolonged exposure to air. The darkening is hastened by the addition of alkali to the urine and is reflected in the original term for homogentisic acid, alkapton, which refers to its avidity for alkali. ...

Alkaptonuria is a rare metabolic disease in which a deficiency of the enzyme homogentisate dioxygenase causes an accumulation of homogentisic acid. Ochronosis consists of excessive deposition of homogentisic acid in the connective tissue and presents as a chestnut brown or black pigmentation. With aging, the accumulation of pigments from homogentisic acid in the joints causes osteoarthrosis. Th...

Alkaptonuria is a rare autosomal recessive disorder of metabolism caused by deficiency of homogentisic acid oxidase and resulting in accumulation of homogentisic acid in collagenous structures. This causes the classic clinical triad: (1) homogentisic aciduria (urine blackens on standing when oxidized or alkalinized); (2) eumelanin-like pigmentation of skin, sclera, cartilages, etc and (3) degen...