Glutaminyl cyclases unfold glutamyl cyclase activity under mild acid conditions

FEBS Lett. 2004 Apr 9;563(1-3):191-6. doi: 10.1016/S0014-5793(04)00300-X.


N-terminal pyroglutamate (pGlu) formation from glutaminyl precursors is a posttranslational event in the processing of bioactive neuropeptides such as thyrotropin-releasing hormone and neurotensin during their maturation in the secretory pathway. The reaction is facilitated by glutaminyl cyclase (QC), an enzyme highly abundant in mammalian brain. Here, we describe for the first time that human and papaya QC also catalyze N-terminal glutamate cyclization. Surprisingly, the enzymatic Glu(1) conversion is favored at pH 6.0 while Gln(1) conversion occurs with an optimum at pH 8.0. This unexpected finding might be of importance for deciphering the events leading to deposition of highly toxic pyroglutamyl peptides in amyloidotic diseases.

Publication types

  • Comparative Study

MeSH terms

  • Aminoacyltransferases / genetics
  • Aminoacyltransferases / metabolism*
  • Aminopeptidases / metabolism
  • Carica / enzymology
  • Carica / metabolism
  • Escherichia coli / enzymology
  • Escherichia coli / metabolism
  • Glutamic Acid / metabolism
  • Glycine / metabolism
  • Humans
  • Hydrogen-Ion Concentration
  • Mass Spectrometry
  • Molecular Structure
  • Pichia / enzymology
  • Pichia / metabolism
  • Protein Denaturation
  • Protein Processing, Post-Translational
  • Recombinant Proteins / metabolism
  • Substrate Specificity


  • Recombinant Proteins
  • Glutamic Acid
  • Aminoacyltransferases
  • glutaminyl-peptide cyclotransferase
  • Aminopeptidases
  • Glycine