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Record Information
StatusDetected and Quantified
Creation Date2005-11-16 15:48:42 UTC
Update Date2020-02-26 21:22:53 UTC
Secondary Accession Numbers
  • HMDB01045
Metabolite Identification
Common NameEnkephalin L
DescriptionEnkephalin L is an opioid peptide. Opioid peptides are a group of neuropeptides which include enkephalins, endorphins and dynorphins. In addition to their central and peripheral antinociceptive function, opioids can modulate immune activity and cell proliferation. Enkephalins typically have a turnover rate measured in seconds to minutes, both in vivo and in vitro, and this stability is related to the age of the cell system under study. It is noteworthy that the residues most essential to enkephalin function are also either neurotransmitters themselves (glycine) or immediate precursors of L-Dopa, dopamine and norepinephrine (tyrosine and phenylalanine). The variable fifth amino acid leucine (leu5) or methionine (met5) has not yet been assigned any neurotransmitter candidacy. Again, this suggests that enkephalin is polyfunctional in that, in its intact state it elicits binding to the same sites in the brain as morphine and other opiates, and its degradation products have a potential for follow-up accessory functions by reacting as signaling entities themselves, or as the immediate precursors to inhibitory or metabotropic neurotransmitters. Enkephalins are present in macrophages infiltrating the dermal papillae in involved psoriatic skin and that the amount of enkephalin is significantly increased in involved psoriatic skin. Major enkephalin pathways in the brain involve the extrapyramidal system, including motor pathways controlled by the basal ganglia, the limbic system that governs emotional and behavioral control, and the hypothalamic-neuroendocrine axis. The apparent overlap of localization within the central nervous system of dopaminergic, glycinergic, and enkephalinergic pathways is speculated to be of neurophysiological significance, especially in light of the relatively short half-life of the enkephalins and the immediate precursor-product relationship between tyrosine and dopamine, and glycinergic signaling. Enkephalins are released into the bloodstream of mammals by the adrenal medulla. Once they are in the blood, these peptides undergo a fairly rapid hydrolysis by several plasma-contained enzymes. However, a fraction of the enkephalins present in the plasma are bound to the serum albumin, and the bound peptides are almost completely intact even after a long incubation in the presence of serum enzymes. (PMID: 9450624 , 16802191 , 4069309 ).
Leucine- enkephalinHMDB
Leucine enkephalinHMDB
[Leu 5]enkephalinHMDB
Enkephalin, 5-leucineHMDB
Leu enkephalinHMDB
5 Leucine enkephalinHMDB
Enkephalin, leucineHMDB
5-Leucine enkephalinHMDB
Chemical FormulaC28H37N5O7
Average Molecular Weight555.6227
Monoisotopic Molecular Weight555.269298563
IUPAC Name(2S)-2-[(2S)-2-(2-{2-[(2S)-2-amino-3-(4-hydroxyphenyl)propanamido]acetamido}acetamido)-3-phenylpropanamido]-4-methylpentanoic acid
Traditional Name(2S)-2-[(2S)-2-(2-{2-[(2S)-2-amino-3-(4-hydroxyphenyl)propanamido]acetamido}acetamido)-3-phenylpropanamido]-4-methylpentanoic acid
CAS Registry Number14-18-6
InChI Identifier
Chemical Taxonomy
Description belongs to the class of organic compounds known as oligopeptides. These are organic compounds containing a sequence of between three and ten alpha-amino acids joined by peptide bonds.
KingdomOrganic compounds
Super ClassOrganic acids and derivatives
ClassCarboxylic acids and derivatives
Sub ClassAmino acids, peptides, and analogues
Direct ParentOligopeptides
Alternative Parents
  • Alpha-oligopeptide
  • Tyrosine or derivatives
  • Phenylalanine or derivatives
  • Leucine or derivatives
  • N-acyl-alpha-amino acid
  • N-acyl-alpha amino acid or derivatives
  • N-acyl-l-alpha-amino acid
  • Alpha-amino acid amide
  • N-substituted-alpha-amino acid
  • Alpha-amino acid or derivatives
  • Amphetamine or derivatives
  • 1-hydroxy-2-unsubstituted benzenoid
  • Phenol
  • Aralkylamine
  • Benzenoid
  • Fatty acyl
  • Monocyclic benzene moiety
  • Fatty amide
  • Secondary carboxylic acid amide
  • Amino acid or derivatives
  • Carboxamide group
  • Amino acid
  • Carboxylic acid
  • Monocarboxylic acid or derivatives
  • Hydrocarbon derivative
  • Primary aliphatic amine
  • Organic oxide
  • Organonitrogen compound
  • Carbonyl group
  • Organooxygen compound
  • Organopnictogen compound
  • Organic nitrogen compound
  • Amine
  • Organic oxygen compound
  • Primary amine
  • Aromatic homomonocyclic compound
Molecular FrameworkAromatic homomonocyclic compounds
External DescriptorsNot Available
Physiological effect

Health effect:


Biological location:


Physical Properties
Experimental Properties
Melting PointNot AvailableNot Available
Boiling PointNot AvailableNot Available
Water SolubilityNot AvailableNot Available
LogPNot AvailableNot Available
Predicted Properties
Water Solubility0.015 g/LALOGPS
pKa (Strongest Acidic)3.7ChemAxon
pKa (Strongest Basic)7.73ChemAxon
Physiological Charge0ChemAxon
Hydrogen Acceptor Count8ChemAxon
Hydrogen Donor Count7ChemAxon
Polar Surface Area199.95 ŲChemAxon
Rotatable Bond Count15ChemAxon
Refractivity145.59 m³·mol⁻¹ChemAxon
Polarizability57.94 ųChemAxon
Number of Rings2ChemAxon
Rule of FiveNoChemAxon
Ghose FilterNoChemAxon
Veber's RuleNoChemAxon
MDDR-like RuleNoChemAxon
Spectrum TypeDescriptionSplash KeyView
Predicted GC-MSPredicted GC-MS Spectrum - GC-MS (Non-derivatized) - 70eV, Positivesplash10-01pc-2913210000-2030f7d4362602946613Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - GC-MS (2 TMS) - 70eV, Positivesplash10-05nf-4193224000-961c021df7886c910304Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 10V, Positivesplash10-0f76-0940020000-01b1154dc17e8249a8c8Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 20V, Positivesplash10-000i-2921000000-331e8269299530ed1230Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 40V, Positivesplash10-000i-2900000000-f5b115db9b594e70d85aSpectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 10V, Negativesplash10-0udi-0222190000-7ff6ef9ac638217877c1Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 20V, Negativesplash10-0043-2985460000-6237cdca7e8b9de1b20dSpectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 40V, Negativesplash10-003u-4952000000-fa381454fd5b34e40546Spectrum
Biological Properties
Cellular LocationsNot Available
Biospecimen Locations
  • Blood
Tissue LocationsNot Available
Normal Concentrations
BloodDetected and Quantified0.00030 (0.00018-0.00056) uMAdult (>18 years old)BothNormal details
Abnormal Concentrations
BloodDetected and Quantified0.00096 (0.00047-0.00290) uMAdult (>18 years old)Both
BloodDetected and Quantified0.0014 (0.0008-0.0024) uMAdult (>18 years old)BothAcute liver disease details
Associated Disorders and Diseases
Disease References
Acute liver disease
  1. Thornton JR, Losowsky MS: Plasma leucine enkephalin is increased in liver disease. Gut. 1989 Oct;30(10):1392-5. [PubMed:2583565 ]
  1. Thornton JR, Losowsky MS: Plasma leucine enkephalin is increased in liver disease. Gut. 1989 Oct;30(10):1392-5. [PubMed:2583565 ]
Associated OMIM IDsNone
DrugBank IDNot Available
Phenol Explorer Compound IDNot Available
FooDB IDFDB022389
KNApSAcK IDNot Available
Chemspider ID406229
KEGG Compound IDNot Available
BioCyc IDNot Available
BiGG IDNot Available
Wikipedia LinkNot Available
METLIN IDNot Available
PubChem Compound461776
PDB IDNot Available
ChEBI ID103389
Food Biomarker OntologyNot Available
VMH IDNot Available
Synthesis ReferenceNot Available
Material Safety Data Sheet (MSDS)Not Available
General References
  1. Nissen JB, Kragballe K: Enkephalins modulate differentiation of normal human keratinocytes in vitro. Exp Dermatol. 1997 Oct;6(5):222-9. [PubMed:9450624 ]
  2. Lukiw WJ: Endogenous signaling complexity in neuropeptides- leucine- and methionine-enkephalin. Cell Mol Neurobiol. 2006 Jul-Aug;26(4-6):1003-10. Epub 2006 Jun 27. [PubMed:16802191 ]
  3. De Marco V, Possenti R, Vita F, Rapposelli B, D'Alagni M, Roda LG: Enkephalin binding systems in human plasma. II: Leu-enkephalin serum albumin interaction. Neurochem Res. 1985 Oct;10(10):1355-69. [PubMed:4069309 ]