Structural correlation between met-enkephalin, an<unk> , (left) and morphine, an opiate drug, (right)<unk> s are peptides that bind to<unk>  receptors in the brain; opiates and<unk> s mimic the effect of these peptides. Such peptides may be produced by the body itself, for example endorphins. The effects of these peptides vary, but they all resemble those of opiates. Brain<unk>  systems are known to play an important role in motivation, emotion, attachment behaviour, the response to stress and pain, and the control of food intake.<unk> -like peptides may also be absorbed from partially digested food (casomorphins, exorphins, and rubiscolins). The<unk>  food peptides have lengths of typically 4–8 amino acids. The body's own<unk> s are generally much longer.<unk> s are released by post-translational proteolytic cleavage of precursor proteins. The precursors consist of the following components: a signal sequence that precedes a conserved region of about 50 residues; a variable-length region; and the sequence of the neuropeptides themselves. Sequence analysis reveals that the conserved N-terminal region of the precursors contains 6 cysteines, which are probably involved in disulfide bond formation. It is speculated that this region might be important for neuropeptide processing.
Opioid peptide
Monoamine neurotransmitter
Serotonin
N-Acetylserotonin
Acetylcholine
Endorphins
Neuropeptide
Heroin