Reaction catalyzed by tRNAHis guanylyltransferase (2.7.7.79)

	pppGp-tRNAHis	+		H2O	=		pGp-tRNAHis	+
	pppGp-tRNAHis	+		H2O	=		pGp-tRNAHis	+		diphosphate