Cysteinyldopaenkephalins: synthesis, characterization and binding to bovine brain opioid receptors.
The reaction of opioid peptides with mushroom tyrosinase in the presence of an excess of a thiol compound gives rise to cysteinyldopaenkephalins (CDEnks). The major product is represented by the 5-S-CDEnk (80%) and the minor one by the isomer 2-S-CDEnk (20%). The adducts between leucine-enkephalin (Leu-enk) and cysteine have been isolated by high performance liquid chromatography (HPLC) and identified by amino acid analysis and electrospray ion mass spectrometry. 5-S-CDEnk is able to bind to opioid receptors in bovine brain membranes. Its binding affinity is higher for delta than for mu receptors and about 8-fold lesser than that exploited by Leu-enk. In the presence of the peroxidase/H(2)O(2) system, CDEnks can be converted into the corresponding pheo-opiomelanins.
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Dipartimento di Scienze Biochimiche 'A. Rossi Fanelli', Università 'La Sapienza', P.le Aldo Moro 5, 00185, Roma, Italy. marosci@axrma.uniroma1.it
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D000701:Analgesics, Opioid / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000737:chemistry; D004743:Enkephalin, Leucine / Q000737:chemistry; D004745:Enkephalins / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D007536:Isomerism; D007700:Kinetics; D013058:Mass Spectrometry; D015394:Molecular Structure; D014442:Monophenol Monooxygenase / Q000737:chemistry; D010084:Oxidation-Reduction; D011957:Receptors, Opioid / Q000378:metabolism*
D000701:Analgesics, Opioid; D004745:Enkephalins; D011957:Receptors, Opioid; C407991:cysteinyldopaenkephalin; D004743:Enkephalin, Leucine; D014442:Monophenol Monooxygenase; D003545:Cysteine