Peptides enkephalins

D Peptides Enkephalins, endorphins, cholecystokinin, substance P (Many others have been implicated)... 

Neprilysin (enkephalinase, Endopeptidase-24.11, neutral endopeptidase, NEP, EC 3.4.24.11) bears considerable resemblance to other zinc-containing metallopeptidases it is an oligopeptidase that hydrolyzes enkephalins and a range of other active peptides. Enkephalins are endogenous ligands of opiate receptors, and the prolongation of their action via inhibition of enkephalinase... 

Impulse traffic in the neo- and pa-leospinothalamic pathways is subject to modulation by descending projections that originate from the reticular formation and terminate at second-order neurons, at their synapses with first-order neurons, or at spinal segmental interneurons (descending antinociceptive system). This system can inhibit impulse transmission from first- to second-order neurons via release of opio-peptides (enkephalins) or monoamines (norepinephrine, serotonin). 

The Use of Carbon-13 NMR to Study Binding of Hormones to Model Receptor Membranes The Opioid Peptide Enkephalin... 

The plant alkaloids mimic the endogenous peptides enkephalins and endorphins (Chapter 12), which meditate nociception and sleep. There are three types of widely distributed opiate receptors. Mu receptors are concentrated in neocortex, striatum, thalamus, hippocampus, amygdala and spinal cord, delta receptors in neocortex and amydala, and kappa receptors in striatum, amygdala and hypothalamus (Mansour et al., 1988). 

We have already discussed the co-occurrence of small amine and peptide neurotransmitters their release is normally Ca + dependent, and they operate through signal transmission. They are also capable of regulating each other s release and even the synthesis, clustering, and affinity of receptors. Neuroendocrine cells are capable of producing more than one peptide, and thus an amine-peptide as well as a peptide-peptide combination is possible. It is known, for instance, that the vagus nerve contains substance P, vasointestinal peptide, enkephalin, cholecystokinin, and somatostatin— peptides with a hybrid combination of neural and hormonal communication properties. 

Figure 3 An approach to the design of a nonpeptide, delta-selective opioid antagonist based on the message-address concept. The message and address components of the delta-selective peptide enkephalin (upper) are compared to those in an opiate (lower).

Simantov R, Kuhar MJ, Uhl GR, Snyder SH (1977) Opioid peptide enkephalin immunohistochemical mapping in rat central nervous system. Proc Natl Acad Sci USA 74 2167-2171. 

In the 1970s, Hughes et al. were the first to show that two very different chemical structures have similar agonist properties (3). The opioid natural product, morphine (3), was found to resemble the N-terminal structure of the endogenous opioid peptides, enkephalins, (4a) and (4b), and j3-endorphin (5) (Fig. 15.2). The remarkable similarity between the morphine phenol system and the IV-terminal tyrosine residue in the peptide opioids implied that these units reacted with opioid receptors in a similar fashion to elicit comparable responses (4-6). 

Fig. 3 Interfacing of pressure-driven CEC (PEC) for the separation of two simple peptides, enkephalin methyl ester (5.58 min) and enkephalin amide (7.39 min), (a) Extracted mass chromatogram of m/z 714 and 729 for the on-line peptide separation. Specific operating conditions are indicated in Ref. 4. (b) Mass spectra taken from the chromatographic peaks in (a), illustrating true and the presence of M+H, M+Na, and M+K cations at appropriate m/z (amu) values. (From Ref. 4 reproduced with permission of the authors and the American Chemical Society.)...

Striatal neurons projection neurons all contain GAD (Aronin et al. 1984 Kita and Kitai 1988 Ribak et al. 1979), although subpopulations contain different neuropeptides including the opiate peptides enkephalin (Beckstead 1985 DiFiglia et al. 1982 Haber and Watson 1983 Hokfelt et al. 1977 Pickel et al. 1980) and dynorphin (Vincent et al. 1982a Vincent et al. 1982b), or the tachykinin substance P (Brownstein et al. 1977 Hong et... 

Some receptors are named after the natural agent, e.g. histamine and 5HT, but others after natural products, the interactions with which were the only means of characterisation before the structures of the true transmitters were known, e.g. opioid after opium (morphine) - the natural ligands here are peptides (enkephalins and endorphins) cannabinoid after cannabis - the natural ligands are amides of arachadonic acid. 

SP, a number of neurotransmitters that are still putative include other neuronal peptides (enkephalins, endorphins) and peptides that act as hormones elsewhere (e.g., angiotensin I and II, prolactin, somatostatin) as well as other amino acids. The number easily exceeds 50 substances, with no end in sight. Other small molecules that may be called the also suggested category include such candidates as ATP, c-AMP, GTP, c-GMP, estrogen, corticosterone, and even several prostaglandins. They will not be considered in this brief overview. 

Simantov R. and Snyder S, H. (1976a) Isolation and structure identification of a morphme-like peptide "enkephalin" in bovine brain Life Set 18,781-788... 

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