214 R. G. WESTALL 
was barely perceptable. Soon after it was found that the keto acid analogues of the 
branched amino acids vz. a-ketoisocaproic, a-keto-$-methylvaleric and a-ketoiso- 
valericacids were excretedin the urine in excessive amounts”®,101,102. There is, therefore, 
a similar state of affairs in this disease as exists in phenylketonuria except that the 
amino acids involved are different and in this newer disease the effects tend to be 
more lethal. Further cases of this disease are frequently being found but so far the 
cause of the metabolic error has not been proved. It is strange that these three amino 
civ 
asa-0 Se 
ASA 
Fig. 15. A paper chromatogram of the urine from a patient with argininosuccinic aciduria. 
acids leucine, isoleucine and valine, and possibly also methionine, all essential amino 
acids to man, should all be involved in the metabolic disturbance. DENT AND WESTALL”? 
carried out a series of dietary experiments on a child with this disease during which 
the intake of the branched amino acids were limited to the minimum requirements 
for growth. The analogous keto acids were no longer excreted and the characteristic 
smell disappeared from the urine. We wondered whether perhaps only one of the 
branched amino acids was truly implicated and that the others were involved by 
some form of transport inhibition. However by feeding the limited amino acids back 
to the diet, in normal amounts, separately and one at a time, we were unable to find 
References p. 217/219 
