ISSN:
0739-4462
Keywords:
cuticular sclerotization
;
N-acylnorepinephrine
;
quinone isornerization
;
P-hydroxylation
;
phenoloxidase
;
quinone isomerase
;
Chemistry
;
Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
Proteins solubilized from the pharate cuticle of Manduca sexta were fractionated by ammonium sulfate precipitation and activated by the endogenous enzymes. The activated fraction readily converted exogenously supplied N-acetyldopamine (NADA) to N-acetylnorepinephrine (NANE). Either heat treatment (70°C for 10 min) or addition of phenylthiourea (2.5 μM) caused total inhibition of the side chain hydroxylation. If chemically prepared NADA quinone was supplied instead of NADA to the enzyme solution containing phenylthiourea, it was converted to NANE. Presence of a quinone trap such as N-acetylcysteine in the NADA-cuticular enzyme reaction not only prevented the accumulation of NADA quinone, but also abolished NANE production. In such reaction mixtures, the formation of a new compound characterized as NADA-quinone-N-acetylcysteine adduct could be readily witnessed. These studies indicate that NADA quinone is an intermediate during the side chain hydroxylation of NADA by Manduca cuticular enzyme(s). Since such a conversion calls for the isomerization of NADA quinone to NADA quinone methide and subsequent hydration of NADA quinone methide, attempts were also made to trap the latter compound by performing the enzymatic reaction in methanol. These attempts resulted in the isolation of β-methoxy NADA (NADA quinone methide methanol adduct) as an additional product. Similarly, when the N-β-alanyldopamine (NBAD)-Manduca enzyme reaction was carried out in the presence of L-kynurenine, two diastereoisomers of NBAD quinone methide-kynurenine adduct ( = papiliochrome IIa and IIb) could be isolated. The above results are in agreement with our hypothesis that N-acylnorepinephrine formed in Manduca cuticle is biosynthesized by an indirect route involving intermediary formation of N-acyldopamine quinone and N-acyldopamine quinone methide as established in the case of Sarcophaga bullata and is not produced by the action of a β-hydroxylase.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/arch.940160205
