On the carbon origin of isovaleric acid residue of urinary isovalthine

FUKUTOME has once reported that isovaleric acid is an isovalthinuria inducer but isovaleric acid-1-C14 administered to a dog does not incorporate into urinary isovalthine and glutamic acid is most strongly labeled among acidic amino acids excreted. Recently, however, KUWAKI has found that liver homogenates of some animals can synthesize C14-labeled S-(isopropylcarboxymethyl) glutathione (GSIV) from isovaleric acid-1-C14 and glutathione, and that GSIV can be converted into isovalthine by kidney homogenate or glutathionase preparation4. For the elucidation of the above discrepancy, FUKUTOME's experiments were repeated by using isovaleric acid-methyl-C14 or-1-C14, and it was again found that these isotopic compounds did not significantly incorporate into urinary isovalthine.