Urinary Excretion of Urocanic Acid and Formimino-glutamic Acid

Abstract

THE major pathway of histidine breakdown is to glutamic acid, and this occurs via two relatively stable intermediate compounds, urocanic acid and formimino-glutamic acid. A competent folic-acid coenzyme is required to accept the formimino-group in the last stage of this pathway. When there is impaired, folic-acid function formimino-glutamic acid accumulates and is excreted in the urine. This has been widely used as a test of folic-acid deficiency in man¹, the urinary excretion of formimino-glutamic acid being measured after an oral dose of 15 g of histidine hydrochloride. The urinary excretion of formiminoglutamic acid after oral doses of histidine may be accompanied by the excretion of urocanic acid². The purpose of this communication is to direct attention to the importance of urocanic acid in the urine of patients with megaloblastic anæmia and other disease states following oral doses of 15 g of histidine hydrochloride.