CPS1 and central nervous system cancer: In fact, N-acetyl-glutamate is an essential allosteric activator of carbamoyl phosphate synthetase 1 (CPS1), so it may be hypothesized that if CPS1 is expressed in the analyzed glioma cell lines, its activation by increased levels of N-acetyl-glutamate might also be responsible for the observed citrulline accumulation.