In enzymology, a N-methyl nucleosidase (EC 3.2.2.25) is an enzyme that catalyzes the chemical reaction

7-methylxanthosine + H₂O 7-methylxanthine + D-ribose

Thus, the two substrates of this enzyme are 7-methylxanthosine and H₂O, whereas its two products are 7-methylxanthine and D-ribose.

This enzyme belongs to the family of hydrolases, specifically those glycosylases that hydrolyse N-glycosyl compounds. The systematic name of this enzyme class is 7-methylxanthosine ribohydrolase. Other names in common use include 7-methylxanthosine nucleosidase, N-MeNase, N-methyl nucleoside hydrolase, and methylpurine nucleosidase.

• Negishi O, Ozawa T, Imagawa H (1988). "N-Methyl nucleosidase from tea leaves". Agric. Biol. Chem. 52: 169–175. doi:10.1271/bbb1961.52.169.