Opioid peptides are converted by mushroom tyrosinase into melanin-like compounds retaining the peptide moiety (opio-melanins). Opio-melanins, owing to the presence of the linked aminoacids and in contrast with DOPA-melanin, are soluble compounds. The enkephalin-generated melanins are cleaved by carboxypeptidase A and pronase whereas aminopeptidase M cannot remove aminoacids from the pigment. Enkephalins, as well as other opioid peptides, (alpha-endorphin, kyotorphin, esorphins) if oxidized in presence of DOPA and tyrosinase are readily incorporated into DOPA-melanin. The resulting mixed-melanins (opio-melanin + DOPA-melanin) can be solubilized in hydrophylic solvents. Melanin from leuenkephalin exhibits paramagnetism as evidenced by an EPR spectrum identical to that of DOPA-melanin, but unlike the latter pigment, it does not appear to oxidize NADH, probably for the presence of the peptide moiety that exerts a hampering effect on the oxidizing capacity.

SOME BIOCHEMICAL-PROPERTIES OF MELANINS FROM OPIOID-PEPTIDES

MUSCI, Giovanni;
1994-01-01

Abstract

Opioid peptides are converted by mushroom tyrosinase into melanin-like compounds retaining the peptide moiety (opio-melanins). Opio-melanins, owing to the presence of the linked aminoacids and in contrast with DOPA-melanin, are soluble compounds. The enkephalin-generated melanins are cleaved by carboxypeptidase A and pronase whereas aminopeptidase M cannot remove aminoacids from the pigment. Enkephalins, as well as other opioid peptides, (alpha-endorphin, kyotorphin, esorphins) if oxidized in presence of DOPA and tyrosinase are readily incorporated into DOPA-melanin. The resulting mixed-melanins (opio-melanin + DOPA-melanin) can be solubilized in hydrophylic solvents. Melanin from leuenkephalin exhibits paramagnetism as evidenced by an EPR spectrum identical to that of DOPA-melanin, but unlike the latter pigment, it does not appear to oxidize NADH, probably for the presence of the peptide moiety that exerts a hampering effect on the oxidizing capacity.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11695/5512
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