Reaction catalyzed by tRNA-guanine15 transglycosylase (2.4.2.48)

	guanine15 in tRNA	+			=		7-cyano-7-deazaguanine15 in tRNA	+
	guanine15 in tRNA	+		7-cyano-7-deazaguanine	=		7-cyano-7-deazaguanine15 in tRNA	+		guanine