The function of GMPR2 (guanosine monophosphate reductase 2, ENSG00000100938) is as follows. Catalyzes the irreversible NADPH-dependent deamination of GMP to IMP. It functions in the conversion of nucleobase, nucleoside and nucleotide derivatives of G to A nucleotides, and in maintaining the intracellular balance of A and G nucleotides (PubMed:12009299, PubMed:12669231, PubMed:16359702, PubMed:22037469). Plays a role in modulating cellular differentiation (PubMed:12669231). {ECO:0000255|HAMAP-Rule:MF_03195, ECO:0000269|PubMed:12009299, ECO:0000269|PubMed:12669231, ECO:0000269|PubMed:16359702, ECO:0000269|PubMed:22037469}.