2-ethyl-3-deuterohydracrylic acid, the major urinary metabolite of 2-trideuteromethylbutyric acid by a new metabolic pathway

The urinary excretion by rats of predominantly 2-ethyl-3-deuterohydracrylic acid is a consequence of the intraperitoneal injection of 2-trideuteromethylbutyric acid. A significant fraction of the loading acid also is excreted unchanged. These results support the proposal of an alternate minor pathway of isoleucine catabolism and suggest that the corresponding catabolites in the minor and major pathways, 2-ethylhydracrylic and 2-methyl-3-hydroxybutyric acids, respectively, have significantly different subsequent metabolism.