Uricotelic metabolism

Uric acid, 2,6,S-trihydroxypmnu an excretory product of purine metabolism in most animals. In some animals, known as uricotelic organisms (birds, reptiles, many insects), it is the main nitrogenous excretory product. U.a. (Af, 168.1, m.p. 400°C) was discovered in urine in 1776 by Scheele, and it can be isolated in quantity from bird excrements (guano) its salts are called urates Humans and the great apes usually excrete U. a. unchanged. In the adult human, 1-3 % of urinary nitrogen is represented by U.a. 

The end products of purine metabolism are uric acid in primates and uricotelic animals, allantoin in mammals other than primates, urea in the rest of the ureotelic animals, and ammonia in many of the ammonotelic animals. 

This species difference may be associated with the fact that birds and mammals differ profoundly in their nitrogenous metabolism the bird being uricotelic, arid excreting waste protein nitrogen as uric acid, whereas the mammal is ureotelic, and excretes nitrogen chiefly as urea (p. 378). 

Uric acid, O6H4N4OJ, the most important of the oxidised purines, is the chief end-product of purine metabolism in man and the higher apes. It is the chief end-product of protein metabolism in uricotelic animals, birds and snakes, and some invertebrates. It is the least soluble of all the forms in which nitrogen is excreted, and appears in calculi, articular deposits, and urinary sediments. 

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