7-N-[(5S)-5-amino-5-carboxypentyl]formamidino-7-deazaguanosine(15) in tRNA + S-adenosyl-L-methionine = archaeosine(15) in tRNA + L-1-piperideine-6-carboxylate + 5'-deoxyadenosine + L-methionine + 2 H(+) — reaction