A novel quinone: quinone methide isomerase generates quinone methides in insect cuticle.
Insoluble cuticle-bound enzyme(s) of Manduca sexta pharate pupae, which is known to convert N-acetyldopamine to N-acetylnorepinephrine through the intermediate formation of quinone methide, also converted exogenously supplied N-acetyldopamine quinone to N-acetylnorepinephrine. The presence of a quinone trap such as N-acetylcysteine in the reaction mixture containing N-acetyldopamine and cuticle prevented the formation of N-acetylnorepinephrine but readily yielded N-acetylcysteine-N-acetyldopamine quinone adduct as a dead-end product. These results indicate the oxidation of N-acetyldopamine to its quinone and its enzyme-catalyzed isomerization to quinone methide before yielding N-acetylnorepinephrine as the stable product. The role of this newly discovered isomerase in sclerotization of insect cuticle is discussed.
Saul
S
S
Department of Biology, University of Massachusetts, Boston 02125.
Sugumaran
M
M
D000818:Animals; D019746:Intramolecular Oxidoreductases; D007535:Isomerases / Q000378:metabolism*; D007700:Kinetics; D007814:Larva; D007915:Lepidoptera / Q000201:enzymology*; D009036:Moths / Q000201:enzymology*; D011809:Quinones / Q000378:metabolism
D011809:Quinones; D007535:Isomerases; D019746:Intramolecular Oxidoreductases; C057265:quinone methide isomerase