The importance of the amido nitrogen to drive cancer cell proliferation has recently been described in glioma, where it was shown that glutamine-derived glutamate had two potential fates: amidation within the glioma cells by glutamine synthase (by using free ammonia) to regenerate glutamine, or export for uptake and amidation by astrocytes.12 This second system permits secretion of the glutamine by astrocytes and uptake by the glioma cells, effectively permitting the astrocytes to fix ammonia from the microenvironment to be utilised for nucleotide synthesis by the tumour. The gene discussed is GLUL; the disease is central nervous system cancer.