Incorporation of Radiolabeled Tyrosine, N-Acetyldopamine, N-β-Alanyldopamine, and the Arylphorin Manducin into the Sclerotized Cuticle of Tobacco Hornworm (Manduca sexta) Pupae

Abstract

Sclerotization of the cuticle depends in many insects on the oxidation of 1 ,2 -diphenolic substrates in the outer parts of the integument. Reactive intermediates such as o-quinones, /?-quinonemethides or free radicals, which may be generated during the oxidative transformations are thought to effect covalent crosslinking of structural proteins by Michael-type additions and/or free radical poly merizations (for a recent review see [1]). Chem ical models are apparently consistent with such theories. However, structures of crosslinks in sclerotized cuticle are essentially unknown due to the difficulties encountered in attempts to isolate soluble deriv atives of native structures from the exoskeleton. Thus, an unambiguous chemical identification of a crosslink partial structure has not been reported with full details. Likewise, very little is known on the identity of structural polypeptides participating in the formation of crosslinks.Applications of immunological [2], radiochem ical [2,3], and histochemical (K. Scheller, personal

Changes in the titer of the female‐predominant storage protein (81K) during larval and pupal development of the waxmoth, galleria mellonella

“…The dramatic declines in 81K levels following larval molts suggest a function for 81K that is related to molting. Thus far the relationship between molting and storage protein metabolism has been shown to involve the incorporation of arylphorin, a class of storage proteins rich in aromatic amino acids [28], into the cuticle [12,13]. The declines in arylphorin that have been measured during larval molting cycles in M. sexta [29] and in Hyalopkora cecropia [28] are consistent with those findings.…”

“…Although storage proteins have been successfully used as model systems, the answers to basic questions concerning their function remain unclear. Studies have provided evidence that they function as a nonspecific amino acid store [ll], as a specific component of the cuticle [12,13] or as a binding protein for ecdysteroids [14] or xenobiotics [15]. Thus, it appears that no single, common function can be ascribed to storage proteins as a class but their abundance and structural homogeneity, even in distantly related species, indicates an important role for storage proteins in insect development.…”

Tyrosine metabolism for insect cuticle tanning

“…During the early stages of hardening of dark-brown cuticle, there is release of tritium from rh~g-[~H]-NADA and @-[3H]-NADA [128]. Other studies have shown that substantial amounts of labeled precursors such as DA or NBAD are covalently bound in dark-brown cuticle by acid-resistant bonds [47,75,134]. These results suggest the o-quinone of NBAD or NADA is an important sclerotization agent in brown cuticle.…”