Chemistry of insect cuticle. 2. The water-insoluble proteins of the cuticle of Aphodius howitti Hope (Coleoptera)

Publisher Website
Google Scholar
Abstract
An examination was made of the protein fractions isolated from the elytra of adult Aphodius howitti which are (1) insoluble in water but soluble in warm dilute alkali, and (2) insoluble in both water and warm dilute alkali. These 2 fractions were analyzed for ash, total N, total S, total carbohydrate and chitin, and the constituent amino-acids and free amino groups were identified. The amino-acids identified in the acid hydrolysates of the fraction soluble in alkali are very similar to those of the water soluble proteins (Hackman, 1953a), the major difference being the absence of proline and hydroxyproline. In both the water-soluble and alkali-soluble proteins the same amino-acids have free amino groups. The fraction insoluble in both water and alkali contained chitin in addition to tanned protein. The tanning reaction introduces much phenolic material. The amino-acids detected on acid hydrolysis are similar to those of the water- and alkali-soluble proteins but serine, threonine and lysine are absent. Free amino groups could not be detected in this material.
Keywords