Purines xanthinuria

The reaction mechanism is incompletely understood. Molybdenum, an essential cofactor, is the initial acceptor of electrons during purine oxidation and undergoes reduction from Mo + to Mo" +. Deficiency of molybdenum can result in xanthinuria. The electrons from molybdenum are passed successively to the iron-sulfur center, to FAD, and finally to oxygen. The oxygen incorporated into xanthine and uric acid originates in water. Xanthine oxidase also yields the superoxide radical, O2, which is then converted to hydrogen peroxide by superoxide dismutase (Chapter 14). This may yield free radicals,... 

In its role in purine catabolism, XnDH catalyzes sequential hydroxylation of the C-2 and C-8 atoms of hypoxanthine, converting it first to xanthine and then to uric acid (eqn (7.1), keto forms shown). In humans, enzyme deficiency is associated with xanthinuria types I and II, the symptoms of which include urinary tract infections, myopathy, arthritis, arthralgia, kidney stones and acute renal failure, while over-activity causes hyperuricemia and the deposition of urate salts in the joints leading to gout. ... 

Uric acid and xanthines are markers for metabolic disorders such as gout, Lesch—Nyman syndrome, and xanthinuria. Measurements of urinary excretion of purine metabolites, among them uric acid and xanthine, have been proposed as a marker for microbial protein synthesis. Their simultaneous determination is useful for diagnosis and treatment of hyperuricemia. In addition to xanthine and hypoxanthine, notable members of the xanthine class include caffeine, theophylhne, and theobromine. ... 

The inherited metabolic disease, xanthinuria, is caused by the absence of xanthine oxidase xanthine and hypoxanthine are excreted instead of uric acid. Gout is caused by an increase in the rate of purine biosynthesis. The resulting increase in the concentration of blood uric add leads to the deposition of crystalline uric add in the joints. 

Xanthinuria see Inborn errors of metabolism. Purine degradation. 

Xanthinuria low uric acid excretion in urine Xanthine oxidase deficiency Ayvazian, J.H., and Skupp, S. The study of purine utilization and excretion in a Xanthinuric man. J. Clin. Invest. 44, 1248-1260 (1965)... 

Xanthinuria is characterized by a large urinary excretion of oxypurine (xanthine + hypoxanthine) which replaces uric acid at the end product of purine metabolism. Patients with xanthinuria are very deficient in xanthine oxidase activity. This rare metabolic disorder may be of interest for both information ... 

Xanthine oxidase is a very important enzyme in the catabolism of purines. In the congenital metaboHc disorder called xanthinuria,... 

In the inborn error, xanthinuria, there is a deficiency of xanthine oxidase, an enzyme involved in the metabolism of purines to uric acid. 

An intermediate in the formation of uric acid from purines. It is excreted in the urine in large amounts in the inborn error of metabolism, xanthinuria, a condition in which xanthine stones can be found. It can be detected in urinary stones by its reaction with Ehrlich s diazo reagent to give a red colour. 

Xanthinuria Insufficient levels of the enzyme xanthine oxidase. Elevated blood and urine levels of xanihlne and hypoxanthine and very low uric acid, a therapeutic xanthinuria accompanies use ot ailopurinol Most cases require no treatment high fluid intake and restricted purine intake recommended. 

Table I. Uric acid and oxypurine excretion in family of patients with xanthinuria. Brackets ( ) indicate values on normal purine diet (see text)...

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