ID   2.7.7.45
DE   guanosine-triphosphate guanylyltransferase.
CA   2 GTP + H(+) = P(1),P(4)-bis(5'-guanosyl) tetraphosphate + diphosphate.
CC   -!- Also acts, more slowly, on GDP to form P(1),P(3)-bis(5'-guanosyl)
CC       triphosphate.
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