A new dopachrome-rearranging enzyme from the ejected ink of the cuttlefish Sepia officinalis.
A melanogenic enzyme catalysing the rearrangement of dopachrome has been identified in the ejected ink of the cuttlefish Sepia officinalis. This enzyme occurs as a heat-labile protein which co-migrates with tyrosinase under a variety of chromatographic and electrophoretic conditions. On SDS/PAGE it shows like a single band with an approx. molecular mass of 85 kDa. The enzyme possesses high substrate specificity, acting on L-dopachrome (Km = 1 mM at pH 6.8) and on L-alpha-methyl-dopachrome, but not on D-dopachrome, L-dopachrome methyl ester, dopaminochrome and adrenochrome. Significant inhibition of the catalytic activity was observed with tropolone and L-mimosine. H.p.1.c. analysis of the enzyme-catalysed rearrangement of L-dopachrome revealed the quantitative formation of the decarboxylated product, 5,6-dihydroxyindole. These results point to marked differences between melanogenesis in cephalopod pigment cells and in melanocytes, which may have important implications in relation to the use of sepiomelanin as a model for studies of mammalian melanins.
Palumbo
A
A
Zoological Station, Villa Comunale, Naples, Italy.
d'Ischia
M
M
Misuraca
G
G
De Martino
L
L
Prota
G
G
D000818:Animals; D002384:Catalysis; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D004798:Enzymes / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D045563:Indolequinones; D007211:Indoles / Q000378:metabolism*; D007700:Kinetics; D008974:Mollusca / Q000201:enzymology*; D009994:Osmolar Concentration; D011809:Quinones / Q000378:metabolism*
D004798:Enzymes; D045563:Indolequinones; D007211:Indoles; D011809:Quinones; C001123:dopachrome; C033871:5,6-dihydroxyindole