ENTRY       EC 2.7.7.45
NAME        Guanosine-triphosphate guanylyltransferase
CLASS       Transferases
            Transferring phosphorus-containing groups
            Nucleotidyltransferases
SYSNAME     GTP:GTP guanylyltransferase
REACTION    2 GTP = Pyrophosphate + P1,P4-Bis(5'-guanosyl) tetraphosphate
SUBSTRATE   GTP
PRODUCT     Pyrophosphate
            P1,P4-Bis(5'-guanosyl) tetraphosphate
COMMENT     Also acts, more slowly, on GDP to form P1,P3-bis(5'-guanosyl)
            triphosphate.
DBLINKS     University of Geneva ENZYME DATA BANK: 2.7.7.45
            WIT (What Is There) Metabolic Reconstruction: 2.7.7.45
///