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ENZYME entry: EC

Accepted Name
E1 SAMP-activating enzyme.
Alternative Name(s)
SAMP-activating enzyme E1.
Reaction catalysed
ATP + [SAMP]-Gly-Gly + [E1 SAMP-activating enzyme]-L-cysteine <=> S-([SAMP]-Gly-Gly)-([E1 SAMP-activating enzyme]-L-cysteine) + AMP + diphosphate
  • The enzyme catalyzes the activation of SAMPs (Small Archaeal Modifier Proteins), which are ubiquitin-like proteins found only in the Archaea.
  • SAMPs are involved in protein degradation, and also act as sulfur carriers involved in thiolation of tRNA and other metabolites such as molybdopterin.
  • The enzyme catalyzes the ATP-dependent formation of a SAMP adenylate intermediate in which the C-terminal glycine of SAMP is bound to AMP via an acyl-phosphate linkage.
  • This intermediate can accept a sulfur atom to form a thiocarboxylate moiety in a mechanism that is not yet understood.
  • Alternatively, the E1 enzyme can transfer SAMP from its activated form to an internal cysteine residue, releasing AMP.
  • In this case SAMP is subsequently transferred to a lysine residue in a target protein in a process termed SAMPylation.
  • Auto-SAMPylation (attachment of SAMP to lysine residues within the E1 enzyme) has been observed.
  • Cf. EC
PRIAM enzyme-specific profiles6.2.1.55
KEGG Ligand Database for Enzyme Nomenclature6.2.1.55
IUBMB Enzyme Nomenclature6.2.1.55
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