A Lipoprotein Precursor of Sclerotin in the Cockroach Cuticle

Abstract

RECENT work has shown that quinone tanning of protein structures is indeed of widespread occurrence in the invertebrates, as was suggested by Dennell¹. The various tanned structures agree in showing a high degree of chemical stability, but the origin of the quinone responsible for tanning has been claimed to differ in different cases². On one hand, in the cockroach ootheca³ and in the blowfly puparium⁴, the quinone has been shown to arise from the enzymatic oxidation of an alcohol-soluble dihydroxyphenol. In certain structures of Mytilus and in the egg cases of Fasciola², on the other hand, it has been suggested that the precursor of the quinone is an alcohol-insoluble amino-acid or protein in which tanning may have evolved through the oxidation of the phenolic hydroxyl groups of tyrosine without removal of the side-chains. A protein, ‘prosclerotin’, rich in phenolic groups has likewise been described in the cuticle of Myriapods⁵, and it has been suggested that this may constitute a similar self-tanning substance.