IUBMB Enzyme Nomenclature


Accepted name: SAMP-activating enzyme

Reaction: ATP + [SAMP]-Gly-Gly = diphosphate + [SAMP]-Gly-Gly-AMP

Glossary: SAMP = small archaeal modifier protein = ubiquitin-like small archaeal modifier protein

Other name(s): UbaA (ambiguous); SAMP-activating enzyme E1 (ambiguous)

Systematic name: ATP:SAMP adenylyltransferase

Comments: Contains Zn2+. The enzyme catalyses the activation of SAMPs (Small Archaeal Modifier Proteins), which are ubiquitin-like proteins found only in the Archaea, by catalysing the ATP-dependent formation of a SAMP adenylate in which the C-terminal glycine of SAMP is bound to AMP via an acyl-phosphate linkage. The product of this activity can accept a sulfur atom to form a thiocarboxylate moiety that acts as a sulfur carrier involved in thiolation of tRNA and other metabolites such as molybdopterin. Alternatively, the enzyme can also catalyse the transfer of SAMP from its activated form to an internal cysteine residue, leading to a process termed SAMPylation (see EC, E1 SAMP-activating enzyme).

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Miranda, H.V., Nembhard, N., Su, D., Hepowit, N., Krause, D.J., Pritz, J.R., Phillips, C., Soll, D. and Maupin-Furlow, J.A. E1- and ubiquitin-like proteins provide a direct link between protein conjugation and sulfur transfer in archaea. Proc. Natl Acad. Sci. USA 108 (2011) 4417-4422. [PMID: 21368171]

2. Maupin-Furlow, J.A. Ubiquitin-like proteins and their roles in archaea. Trends Microbiol 21 (2013) 31-38. [PMID: 23140889]

3. Hepowit, N.L., de Vera, I.M., Cao, S., Fu, X., Wu, Y., Uthandi, S., Chavarria, N.E., Englert, M., Su, D., Sll, D., Kojetin, D.J. and Maupin-Furlow, J.A. Mechanistic insight into protein modification and sulfur mobilization activities of noncanonical E1 and associated ubiquitin-like proteins of Archaea. FEBS J. 283 (2016) 3567-3586. [PMID: 27459543]

[EC created 2018]

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