EC	2.6.1.97
Accepted name:	archaeosine synthase
Reaction:	L-glutamine + 7-cyano-7-carbaguanine15 in tRNA + H2O = L-glutamate + archaeine15 in tRNA
Glossary:	7-cyano-7-carbaguanine = preQ0 = 7-cyano-7-deazaguanine archaeine = 7-deaza-7-carbamidoylguanine = base G* archaeosine = G* = 7-amidino-7-deazaguanosine
Other name(s):	ArcS; TgtA2; MJ1022 (gene name); glutamine:preQ0-tRNA amidinotransferase (incorrect)
Systematic name:	L-glutamine:7-cyano-7-carbaguanine aminotransferase
Comments:	In Euryarchaeota the reaction is catalysed by ArcS [1,2]. In Crenarchaeota, which do not have an ArcS homologue, the reaction is catalysed either by a homologue of EC 6.3.4.20, 7-cyano-7-deazaguanine synthase that includes a glutaminase domain (cf. EC 3.5.1.2), or by a homologue of EC 1.7.1.13, preQ1 synthase [2]. The enzyme from the Euryarchaeon Methanocaldococcus jannaschii can also use arginine and ammonium as amino donors.
References:	1.  Phillips, G., Chikwana, V.M., Maxwell, A., El-Yacoubi, B., Swairjo, M.A., Iwata-Reuyl, D. and de Crecy-Lagard, V. Discovery and characterization of an amidinotransferase involved in the modification of archaeal tRNA. J. Biol. Chem. 285 (2010) 12706–12713. [PMID: 20129918] 2.  Phillips, G., Swairjo, M.A., Gaston, K.W., Bailly, M., Limbach, P.A., Iwata-Reuyl, D. and de Crecy-Lagard, V. Diversity of archaeosine synthesis in crenarchaeota. ACS Chem. Biol. 7 (2012) 300–305. [PMID: 22032275]
[EC 2.6.1.97 created 2012]