rRNA N-glycosylase (, ribosomal ribonucleate N-glycosidase, nigrin b, RNA N-glycosidase, rRNA N-glycosidase, ricin, momorcochin-S, Mirabilis antiviral protein, gelonin, saporins) is an enzyme with systematic name rRNA N-glycohydrolase. This enzyme catalyses the following chemical reaction
Ricin A-chain and related toxins show this activity. The only protein family known to have this activity is the ribosome-inactivating protein (RIP) family.