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  • 1
    Electronic Resource
    Electronic Resource
    Biosynthesis of dehydro-N-acetyldopamine by a soluble enzyme preparation from the larval cuticle of Sarcophaga bullata involves intermediary formation of N-acetyldopamine quinone and N-acetyldopamine quinone methide (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 15 (1990), S. 237-254 
    Details
    ISSN: 0739-4462
    Keywords: phenoloxidase ; quinone isomerase ; quinone methide isomerase ; β-sclerotization ; quinone methide sclerotization ; side chain desaturation ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The enzymes involved in the side chain hydroxylation and side chain desaturation of the sclerotizing precursor N-acetyldopamine (NADA) were obtained in the soluble form from the larval cuticle of Sarcophaga bullata and the mechanism of the reaction was investigated. Phenylthiourea, a well-known inhibitor of phenoloxidases, drastically inhibited both the reactions, indicating the requirement of a phenoloxidase component. N-acetylcysteine, a powerful quinone trap, trapped the transiently formed NADA quinone and prevented the production of both N-acetylnorepinephrine and dehydro NADA. Exogenously added NADA quinone was readily converted by these enzyme preparations to N-acetylnorepinephrine and dehydro NADA. 4-Alkyl-o-quinone:2-hydroxy-p-quinone methide isomerase obtained from the cuticular preparations converted chemically synthesized NADA quinone to its quinone methide. The quinone methide formed reacted rapidly and nonezymatically with water to form N-acetylnorepinephrine as the stable product. Similarly 4-(2-hydroxyethl)-o-benzoquinone was converted to 3,4-dihydroxyphenyl glycol. When the NADA quinone-quinone isomerase reaction was performed in buffer containing 10% methanol, β-methoxy NADA was obtained as an additional product. Furthermore, the quinones of N-acetylnorepinephrine and 3,4-dihydroxyphenyl glycol were converted to N-acetylarterenone and 2-hydroxy-3′,4′-dihydroxyacetophenone, respectively, by the enzyme. Comparison of nonenzymatic versus enzymatic transformation of NADA to N-acetylnorepinephrine revealed that the enzymatic reaction is at least 100 times faster than the nonezymatic rate. Resolution of the NADA desaturase system on Benzamidine Sepharose and Sephacryl S-200 columns yielded the above-mentioned quinone isomerase and NADA quinone methide:dehydro NADA isomerase. The latter, on reconstitution with mushroom tyrosinase and hemolymph quinone isomerase, catalyzed the biosynthesis of dehydro NADA from NADA with the intermediary formation of NADA quinone and NADA quinone methide.The results are interpreted in terms of the quinone methide model elabrated by our group [Sugumaran: Adv. Insect Physiol. 21 :179-231, 1988; Sugumaran et al.: Arch. Insect Biochem. Physiol. 11 :109,1989] and it i s concluded that the two enzyme p-sclerotization model [Andersen: Insect Biochem. 19:59-67,375-382,1989] is inadequate to account for various observations made on insect cuticle.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940150405
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  • 2
    Electronic Resource
    Electronic Resource
    Studies on the enzymes involved in puparial cuticle sclerotization in Drosophila melanogaster (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 19 (1992), S. 271-283 
    Details
    ISSN: 0739-4462
    Keywords: quinone tanning ; quinone methide sclerotization ; β-sclerotization ; phenoloxidase ; quinone isomerase ; quinone methide isomerase ; dehydro-N-acetyldopamine ; fruit fly ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The properties of cuticular enzymes involved in sclerotization of Drosophila melanogaster puparium were examined. The cuticle-bound phenoloxidase from the white puparium exhibited a pH optimum of 6.5 in phosphate buffer and oxidized a variety of catecholic substrates such as 4-methylcatechol, N-β-alanyldopamine, dopa, dopamine, N-acetyldopamine, catechol, norepinephrine, 3,4-dihydroxyphenylglycol, 3,4-dihydroxylbenzoic acid, and 3,4-dihydroxyphenylacetic acid. Phenoloxidase inhibitors such as potassium cyanide and sodium fluoride inhibited the enzyme activity drastically, but phenylthiourea showed marginal inhibition only. This result, coupled with the fact that syringaldazine served as the substrate for the insoluble enzyme, confirmed that cuticular phenoloxidase is of the “laccase” type. In addition, we also examined the mode of synthesis of the sclerotizing precursor, 1,2-dehydro N-acetyldopamine. Our results indicate that this catecholamine derivative is biosynthesized from N-acetyldopamine through the intermediate formation of N-acetyldopamine quinone and N-acetyldopamine quinone methide as established for Sarcophage bullata [Saul, S. and Sugumaran, M., F.E.B.S. Letters 251, 69-73 (1989)]. Accordingly, successful solubilization and fractionation of cuticular enzymes involved in the introdution of a double bond in the side chain of N-acetyldopamine indicated that they included o-diophenoloxidase, 4-alkyl-o-quinone: p-quinone methide isomerase, and N-acetyldopamine quinone methide: dehydro N-acetyldopamine isomerase and not any side chain desaturase. © 1992 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940190406
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  • 3
    Electronic Resource
    Electronic Resource
    On the oxidation of 3,4-dihydroxyphenethyl alcohol and 3,4-dihydroxyphenyl glycol by cuticular enzyme(s) from Sarcophaga bullata (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 10 (1989), S. 13-27 
    Details
    ISSN: 0739-4462
    Keywords: insect cuticle ; catecholamine metabolism ; quinone methide sclerotization ; quinone tanning ; phenoloxidase ; quinone tautomerase ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The catabolic fate of 3,4-dihydroxyphenethyl alcohol (DHPA) and 3,4-dihydroxyphenylethyl glycol (DHPG) in insect cuticle was determined for the first time using cuticular enzyme(s) from Sarcophaga bullata and compared with mushroom tyrosinase-medicated oxidation. Mushroom tyrosinase converted both DHPA and DHPG to their corresponding quinone derivatives, while cuticular enzyme(s) partly converted DHPA to DHPG. Cuticular enzyme(s)-mediated oxidation of DHPA also accompanied the covalent binding of DHPA to the cuticle. Cuticle-DHPA adducts, upon pronase digestion, released peptides that had bound catechols. 3,4-Dihydroxyphenyl-acetaldehyde, the expected product of side chain desaturation of DHPA, was not formed at all. The presence of N-acetylcysteine, a quinone trap, in the reaction mixture containing DHPA and cuticle resulted in the generation of DHPA-quinone-N-acetylcysteine adduct and total inhibition of DHPG formation. The insect enzyme(s) converted DHPG to its quinone at high substrate concentration and to 2-hydroxy-3′,4′-dihydroxyacetophenone at low concentration. They converted exogenously added DHPA-quinone to DHPG, but acted sluggishly on DHPG-quinone. These results are consistent with the enzymatic transformations of phenoloxidase-generated quinones to quinone methides and subsequent nonenzymatic transformation of the latter to the observed products. Thus, quinone methide formation in insect cuticle seems to be caused by the combined action of two enzymes, phenoloxidase and quinone tautomerase, rather than the action of quinone methide-generating phenoloxidase (Sugumaran: Arch Insect Biochem Physiol 8, 73-88, 1988). It is proposed that DHPA and DHPG in combination can be used effectively to examine the participation of (1) quinone, (2) quinone methide, and (3) dehydro derivative intermediates in the metabolism of 4-alkylcatechols for cuticular sclerotization.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940100103
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  • 4
    Electronic Resource
    Electronic Resource
    On the mechanism of side chain oxidation of N-β-alanyldopamine by cuticular enzymes from Sarcophaga bullata (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 15 (1990), S. 255-269 
    Details
    ISSN: 0739-4462
    Keywords: quinone methide sclerotization ; quinone tanning ; β-sclerotization ; catecholamine oxidation ; papiliochrome biosynthesis ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The metabolism of N-β-alanyldopamine (NBAD) by Sarcophaga bullata was investigated. Incubation of NBAD with larval cuticular preparations resulted in the covalent bindings of NBAD to the cuticle and generation of N-β-alanylnorepinephrine (NBANE) as the soluble product. When the reaction was carried out in presence of a powerful quinone trap viz., N-acetylcysteine, NBANE formation was totally abolished; but a new compound characterized as NBAD-quinone-N-acetylcysteine adduct was generated. These results indicate that NBAD quinone is an obligatory intermediate for the biosynthesis of NBANE in sarcophagid cuticle. Accordingly, phenylthiourea - a well-known phenoloxidase inhibitor - completely inhibited the NBANE production even at 5 μM level. A soluble enzyme isolated from cuticle converted exogenously supplied NBAD quinone to NBANE. Chemical considerations indicated that the enzyme is an isomerase and is converting NBAD quinone to its quinone methide which was rapidly and nonenzymatically hydrated to form NBANE. Consistent with this hypothesis is the finding that NBAD quinone methide can be trapped as β-methoxy NBAD by performing the enzymatic reaction in 10% methanol. Moreover, when the reaction was carried out in presence of kynurenine, two diastereoisomeric structures of papiliochrome II-{Nar-[α-3-aminopropionyl amino methyl-3,4-dihydroxybenzyl]-L-kynurenine} could be isolated as byproducts, indicating that the further reactions of NBAD quinone methide with exogenously added nucleophiles are nonenzymatic and nonstereoselective. Based on these results, it is concluded that NBAD is metabolized via NBAD quinone and NBAD quinone methide by the action of phenoloxidase and quinone isomerase respectively. The resultant NBAD quinone methide, being highly reactive, undergoes nonenzymatic and nonstereoselective Michael-1,6-addition reaction with either water (to form NBANE) or other nucleophiles in cuticle to account for the proposed quinone methide sclerotization.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940150406
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