Has low, barely detectable phosphoribosyltransferase activity (in vitro). Binds GMP, IMP and alpha-D-5-phosphoribosyl 1-pyrophosphate (PRPP). Is not expected to contribute to purine metabolism or GMP salvage. This is the function of PRTFDC1 (phosphoribosyl transferase domain containing 1, ENSG00000099256).