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Vertebrate endogenous opioids neuropeptides are released by post-translational
proteolytic processing of precursor proteins. These precursor proteins consist
of a signal sequence followed by a conserved region of about 50 residues, a
variable length region and the sequence of the various neuropeptides. Three
types of precursors are currently known:
Preproenkephalin A (gene PENK) which is processed to produce the peptides
Met-enkephalin (6 copies) and Leu-enkephalin,
Preproenkephalin B (gene PDYN) which is processed to produce the peptides
neoendorphin, dynorphin, leumorphin, rimorphin and leu-enkephalin.
Prepronocipeptin (gene PNOC) which is processed to produce the peptides
nociceptin (orphanin FQ) as well as two other potential neuropeptides.
The conserved region in the N-terminal of these precursors contains six
cysteines that are probably involved in disulfide bonds. This region could be
important for the processing of the neuropeptides .
May 2004 / Text revised.
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