Glutamate entering into the brain along with ammonia transforms into the following amino acid:

The brain's uptake of glutamate is approximately balanced by its output of glutamine. Glutamate entering the brain associates with ammonia and leaves as glutamine. The glutamate--glutamine conversion in the brain--the opposite of the reaction in the kidney that produces some of the ammonia entering the tubules--serves as a detoxifying mechanism to keep the brain free of ammonia. Ammonia is very toxic to nerve cells, and ammonia intoxication is believed to be a major cause of the bizarre neurologic symptoms in hepatic coma. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 33. Circulation through Special Regions. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.