Metabolic origin of 3,4-dihydroxyphenylacetic acid in Tenebrio molitor and differences in its content in larval, pupal, and adult cuticle

Abstract

Pupal exuviae from Tenebrio molitor differ from larval exuviae and adult cuticle in that they lack 3,4-dihydroxyphenylacetic acid (3,4-DPA), a phenolic compound thought to be characteristic of coleopteran cuticle. This difference is not due to an absence of all cuticular o-dihydricphenols since all three cuticles yield comparable amounts of ketocatechol. The significance of this previously unreported stage difference is discussed in the light of the various functions proposed for 3,4-DPA in insect cuticle. Tyrosine is shown to be the primary precursor of 3,4-DPA in adult cuticle. Dopamine and N-acetyldopamine appear to make only a minor contribution to its formation.