The functional significance of these enzymatic reactions is underscored by the observation that overexpression of MYCN markedly sensitizes non-MYCN-amplified neuroblastoma cells to the glutamine analogue DON (6-diazo-5-oxo-L-norleucine), which blocks the conversion of glutamine to glutamate by inhibiting glutamine amidotransferases [66]. Here, GMPS is linked to neuroblastoma.