| Comments |
The enzyme, which is specific for GTP, was characterized from the archaeon?Pyrococcus furiosus. The enzyme converts the 3′-terminal phosphate of various RNA substrates into the 2′,3′-cyclic phosphodiester in a GTP-dependent reaction. Catalysis occurs by a three-step mechanism, starting with the activation of the enzyme by GTP, forming a phosphoramide bond between guanylate and a histidine residue. The guanylate group is then transferred to the 3′-phosphate terminus of the substrate, forming the capped structure [RNA]-3′-(5′-diphosphoguanosine). Finally, the enzyme catalyses an attack of the vicinal O-2′ on the 3′-phosphorus, which results in formation of cyclic phosphate and release of the guanylate.?cf. EC?6.5.1.4, RNA-3′-phosphate cyclase (ATP). |
