Specifically hydrolyzes 7-methylguanosine monophosphate (m(7)GMP) to 7-methylguanosine and inorganic phosphate (, ). The specific activity for m(7)GMP may protect cells against undesired salvage of m(7)GMP and its incorporation into nucleic acids . Also has weak activity for CMP (, ). UMP and purine nucleotides are poor substrates .
Subcellular locations: Cytoplasm