11/12/2023 0 Comments Incontrol 24 bladder reviewsIn birds and reptiles, and in some desert-dwelling mammals (such as the kangaroo rat), uric acid also is the end product of purine metabolism, but it is excreted in feces as a dry mass. The Dalmatian has a genetic defect in uric acid uptake by the liver and kidneys, resulting in decreased conversion to allantoin, so this breed excretes uric acid, and not allantoin, in the urine. Normal excretion of uric acid in the urine is 270 to 360 mg per day (concentration of 270 to 360 mg/L if one litre of urine is produced per day – higher than the solubility of uric acid because it is in the form of dissolved acid urates), roughly 1% as much as the daily excretion of urea. In humans, about 70% of daily uric acid disposal occurs via the kidneys, and in 5–25% of humans, impaired renal (kidney) excretion leads to hyperuricemia. An individual can have serum values as high as 96 mg/L and not have gout. The normal concentration range of uric acid (or hydrogen urate ion) in human blood is 25 to 80 mg/L for men and 15 to 60 mg/L for women (but see below for slightly different values). In humans, over half the antioxidant capacity of blood plasma comes from hydrogen urate ion. Both uric acid and ascorbic acid are strong reducing agents ( electron donors) and potent antioxidants. The loss of uricase in higher primates parallels the similar loss of the ability to synthesize ascorbic acid, leading to the suggestion that urate may partially substitute for ascorbate in such species. In humans and other great apes, uric acid (actually hydrogen urate ion) is the final oxidation (breakdown) product of purine metabolism and is excreted in urine, whereas in most other mammals, the enzyme uricase further oxidizes uric acid to allantoin. Genetic and physiological diversity Primates Uric acid is released in hypoxic conditions (low oxygen saturation). Xanthine oxidase is a large enzyme whose active site consists of the metal molybdenum bound to sulfur and oxygen. ) Xanthine in turn is produced from other purines. XO, which is found in mammals, functions primarily as a dehydrogenase and rarely as an oxidase, despite its name. The enzyme xanthine oxidase (XO) catalyzes the formation of uric acid from xanthine and hypoxanthine. The lower the number, the more soluble the substance in the said solvent. The figures given indicate what mass of water is required to dissolve a unit mass of compound indicated. Solubility of urate salts (grams of water per gram of compound) In ethanol/water mixtures, the solubilities are somewhere between the end values for pure ethanol and pure water. The solubility of the acid and its salts in ethanol is very low or negligible. This low solubility is significant for the etiology of gout. All these salts exhibit greater solubility in hot water than cold, allowing for easy recrystallization. In general, the water solubility of uric acid and its alkali metal and alkaline earth salts is rather low. Thus at physiological pH, urate predominates in solution. Uric acid is a diprotic acid with p K a1 = 5.4 and p K a2 = 10.3. Uric acid crystallizes in the lactam form, with computational chemistry also indicating that tautomer to be the most stable. Uric acid displays lactam–lactim tautomerism. In 1882, the Ukrainian chemist Ivan Horbaczewski first synthesized uric acid by melting urea with glycine. Uric acid was first isolated from kidney stones in 1776 by Swedish chemist Carl Wilhelm Scheele. High blood concentrations of uric acid can lead to gout and are associated with other medical conditions, including diabetes and the formation of ammonium acid urate kidney stones. Uric acid is a product of the metabolic breakdown of purine nucleotides, and it is a normal component of urine. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C 5H 4N 4O 3.
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