The PsiMP glycosidase biologically has a cleavage function and catalyzes the reversible cleavage of the C-C glycoside bond to form ribose-5-phosphate and uracil. PsiMP glycosidase, together with the enzyme pseudouridine kinase, is responsible for the degradation of pseudouridine in E. coli.
The enzymes PsiMP glycosidase and pseudouridine kinase are encoded by separate genes in bacterial genomes. PsiMP glycosidase is encoded by the yeiN gene, and pseudouridine kinase is encoded by the yeiC gene. Both genes belong to the same operon. In humans and other higher organisms, pseudouridine kinase and PsiMP glycosidase are not found. However, they are present in some eukaryotes as the only bifunctional enzymes. In the process of pseudouridine degradation, when pseudouridine kinase phosphorylates pseudouridine, pseudouridine 5'-phosphate (PsiMP) is formed as a degradation product of RNAs. PsiMP is a non-classical nucleoside that has a glycosidic C-C bond and is present in human urine.