Reactome: A Curated Pathway Database

Hydrolysis of the 5'-end of the nascent transcript by the capping enzyme (R-HSA-77078) [Homo sapiens]


After the capping complex is formed, the RNA triphosphatase activity of the capping enzyme hydrolyzes the 5'-end phosphate group of the nascent mRNA transcript to a diphosphate.
The RNA triphosphatase (RTP) domain of mammalian capping enzyme is a member of a superfamily of phosphatases that include the protein tyrosine phosphatases, some lipid phosphatases, and several nucleic acid phosphatases. This family uses a conserved nucleophilic cysteine residue to attack the target phosphate. A transient phospho-cysteinyl enzyme intermediate is then hydrolyzed to regenerate the enzyme active site. It should be noted that while higher eukaryotic capping enzymes use PTP-like triphosphatase domains, the yeast triphosphatases are a completely different class of enzymes. The yeast RTPs are metal-dependent phosphatases. RNA 5'-triphosphatase (RTP) catalyzed first reaction can be represented as:pppN(pN)n + GTP -> ppN(pN)n + Pi; (n=20-25)

Additional Information
Compartment nucleoplasm
Components of this entry
Input entries
Output entries
Catalyst Activity
PhysicalEntity Activity Active Units
Capping complex (initial) polynucleotide 5'-phosphatase activity (0004651)
Literature References
pubMedId Title Journal Year
9512541 Isolation and characterization of a human cDNA for mRNA 5'-capping enzyme. Nucleic Acids Res 1998
Inferred Entries
Orthologous events