Since the human kidney cortex is devoid of GS activity [20] and urea cycle enzyme activities in the liver do not show changes reflecting inability of the liver to detoxify ammonia during VPA-induced hyperammonemia [21], the removal of excessive NH4 through incorporation into glutamine by glutamine synthetase (GS) enzyme in the liver and brain should be examined. The gene discussed is GLUL; the disease is Hyperammonemia.