Kyotorphin (tyrosine-arginine) synthetase in rat brain synaptosomes

J Biol Chem. 1987 Jun 15;262(17):8165-73.


Kyotorphin (Tyr-Arg) is a unique neuropeptide which produces analgesia by releasing Met-enkephalin from slices of the brain and spinal cord. Recent studies revealed that kyotorphin possesses the properties of neurotransmitter/neuroregulator. In the present study, we identified a kyotorphin synthetase in the soluble fraction of rat brain synaptosomes (synaptosol) and characterized it. The enzyme partially purified with Sephacryl S-300 showed an absolute requirement for ATP, MgCl2, tyrosine, and arginine. The optimal pH was 7.5-9.0 and the pI was determined to be 6.1-6.2 by isoelectric focusing. The Km was 25.6 microM for tyrosine, 926 microM for arginine, 294 microM for ATP, and 442 microM for MgCl2. The Vmax was 34.0 pmol/mg of protein/h. The apparent molecular size of this "kyotorphin synthetase" further purified by the DE52 column was 240,000-245,000 daltons, estimated using TSKgel G4000SW column chromatography. The enzyme reaction is represented by the following equation: Tyr + Arg + ATP + MgCl2 + kyotorphin synthetase----Tyr-Arg (kyotorphin) + AMP + PPi + MgCl2 + kyotorphin synthetase. The regional distribution and subcellular localization of the synthetase showed a close correlation to that of kyotorphin levels in the rat brain. The amounts of kyotorphin formed from amino acids by the synthetase in the dialyzed synaptosol was 3.0-4.0 times higher than that from precursor proteins by processing enzymes within the 30 min incubation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics
  • Brain / enzymology*
  • Cross Reactions
  • Endorphins / analysis
  • Immune Sera
  • Kinetics
  • Molecular Weight
  • Peptide Synthases / isolation & purification
  • Peptide Synthases / metabolism*
  • Substrate Specificity
  • Synaptosomes / enzymology*


  • Analgesics
  • Endorphins
  • Immune Sera
  • kyotorphin
  • Peptide Synthases
  • kyotorphin synthetase