N-acetyldopamine quinone methide/1,2-dehydro- N-acetyl dopamine tautomerase : A new enzyme involved in sclerotization of insect cuticle

The enzyme system causing the side chain desaturation of the sclerotizing precursor, N-acetyldopamine (NADA), was solubilized from the larval cuticle of Sarcophaga bullata and resolved into three components. The first enzyme, phenoloxidase, catalyzed conversion of NADA to NADA quinone and provided i...

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Bibliographic Details
Published in:FEBS letters 1989-09, Vol.255 (2), p.340-344
Main Authors: Saul, Steven J., Sugumaran, Manickam
Format: Article
Language:English
Subjects:
Animals
Catechol Oxidase - metabolism
Catecholamine
Chromatography, Gel
Cuticular sclerotization
Diptera
Diptera - enzymology
Diptera - physiology
Dopamine - analogs & derivatives
Dopamine - metabolism
Intramolecular Oxidoreductases
Isomerases - isolation & purification
Isomerases - metabolism
Kinetics
Larva
Oxidoreductases - metabolism
Quinone isomerase
Quinone methide
Quinone methide isomerase
Sarcophaga bullata
Sarcophagidae
Side chain desaturation
Spectrophotometry, Ultraviolet
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Summary:The enzyme system causing the side chain desaturation of the sclerotizing precursor, N-acetyldopamine (NADA), was solubilized from the larval cuticle of Sarcophaga bullata and resolved into three components. The first enzyme, phenoloxidase, catalyzed conversion of NADA to NADA quinone and provided it for the second enzyme (NADA quinone isomerase), which makes the highly unstable NADA quinone methide. Quinone methide was hydrated rapidly and nonenzymatically to form N-acetylnorepinephrine. In addition, it also served as the substrate for the last enzyme, quinone methide tautomerase, which converted it to 1,2-dehydro-NADA. Reconstitution of NADA side chain desaturase activity was achieved by mixing the last enzyme fraction with NADA quinone isomerase, obtained from the hemolymph of the same organism, and mushroom tyrosinase. Therefore, NADA side chain desaturation observed in insects is caused by the combined action of three enzymes rather than the action of a single specific NADA desaturase, as previously thought.
ISSN:0014-5793
1873-3468
DOI:10.1016/0014-5793(89)81117-2