title: Kyotorphin (tyrosine-arginine) synthetase in rat brain synaptosomes.
abstract: 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.
mesh_terms: D000700:Analgesics; D001921:Brain / Q000201:enzymology*; D003429:Cross Reactions; D004723:Endorphins / Q000032:analysis; D007106:Immune Sera; D007700:Kinetics; D008970:Molecular Weight; D010453:Peptide Synthases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013574:Synaptosomes / Q000201:enzymology*
chemical_list: D000700:Analgesics; D004723:Endorphins; D007106:Immune Sera; C019448:kyotorphin; D010453:Peptide Synthases; C052769:kyotorphin synthetase