| Abstract: | The validity of Pryor's widely accepted quinone tanning hypothesis for the sclerotization of insect cuticle was examined using an in vitro model system. Quinones generated in situ by the oxidation of catechols with mushroom tyrosinase and molecular oxygen readily reacted with test proteins such as lysozyme, ribonuclease and cytochrome-c, producing dimers, trimers, and higher oligomers. With the exception of 3,4-dihydroxyphenylalanine, dopamine, and norepinephrine, most other catechols tested participated in protein polymerization. The inability of these three compounds to support oligomerization of test protein was attributed to their high rate of intramolecular cyclization reaction. Radioactive incorporation studies reveal the formation of catechol-protomer adducts, as well as aryl-protein crosslinks in the reaction mixture. The above results strongly support the quinone tanning hypothesis. Based on these findings, the mechanism of cuticular sclerotization is discussed. |
