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...

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Bibliographic Details
Published in:Biochemical journal 1994-05, Vol.299 (3), p.839-844
Main Authors: PALUMBO, A, D'ISCHIA, M, MISURACA, G, DE MARTINO, L, PROTA, G
Format: Article
Language:English
Subjects:
Analytical, structural and metabolic biochemistry
Animals
Biological and medical sciences
Catalysis
Cephalopoda
Chromatography, Gel
Chromatography, High Pressure Liquid
Chromatography, Ion Exchange
Electrophoresis, Polyacrylamide Gel
Enzymes - isolation & purification
Enzymes - metabolism
Enzymes and enzyme inhibitors
Fundamental and applied biological sciences. Psychology
Hydrogen-Ion Concentration
Indolequinones
Indoles - metabolism
Kinetics
Marine
Miscellaneous
Mollusca - enzymology
Osmolar Concentration
Quinones - metabolism
Sepia officinalis
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Summary: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.
ISSN:0264-6021
1470-8728
DOI:10.1042/bj2990839