mRNA guanylyltransferase

In enzymology, a mRNA guanylyltransferase (EC2.7.7.50) is an enzyme that catalyzes the chemical reaction

Thus, the two substrates of this enzyme are GTP and (5')ppPur-mRNA, whereas its two products are diphosphate and G(5')pppPur-mRNA.

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is GTP:mRNA guanylyltransferase. Other names in common use include mRNA capping enzyme, messenger RNA guanylyltransferase, and Protein 2.