Glutamine in the blood, as previously pointed out in these columns,1 is the source of the ammonia in the urine. The functional importance of ammonia as the endogenous base makes this fact especially significant in metabolism. Glutamine, an acid amide, is a constituent of the protein molecule. It may occur free in certain tissues, as indicated by its discovery in horse meat extract in a study2 which, furthermore, proved its indispensability for the growth of the hemolytic streptococcus.
Glutamine is also present in body fluids. In 1942 Hamilton3 pointed out that in picric acid filtrates of human and canine plasma there is present an organic compound containing nitrogen which behaves strikingly like glutamine when heated at an acid reaction. Shortly thereafter another report4 called attention to a glutamine-like substance in the protein free filtrate of plasma and serum of man and rabbit in a concentration of