Reactome: A Curated Pathway Database

Hydrolysis of the 5'-end of the nascent transcript by the capping enzyme

Stable Identifier
Homo sapiens
Locations in the PathwayBrowser

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)

Literature References
PubMed ID Title Journal Year
Participant Of
This entity is regulated by:
Title Physical Entity Activity
polynucleotide 5'-phosphatase activity of Capping complex (initial) [nucleoplasm] Capping complex (initial) [nucleoplasm] polynucleotide 5'-phosphatase activity (0004651)
Orthologous Events