Cyanoglucoside storing cuticle of Zygaena Larvae (Insecta,Lepidoptera)

Summary As a deterrent against predators, larvae of Zygaena trifolii release droplets of fluid containing cyanoglucosides from segmentally arranged cuticular cavities. Histological examinations show that during the moulting period, the old cuticle, including the cavities and the secretion within them, is degraded, with the exception of a thin mesocuticular layer forming the exuviae. When the endocuticular layer of the new cuticle is deposited, the cuticle detaches from the underlying epidermis in specific areas, which leads to the formation of the cuticular cavities. During a moult-intermoult sequence the concentration of cyanoglucosides in both the haemolymph and the defensive secretion shows specific changes. These changes seem to be related to the formation and degradation of the cavities. We suggest that during the moult the cyanoglucosides are transported through the epidermis into the haemolymph to prevent them from being wasted with the exuviae and, after ecdysis, are retranslocated into the newly formed cavities.     

Qualitative and quantitative studies on the compounds of the larval defensive secretion of Zygaena trifolii (Esper, 1783) (Insecta, Lepidoptera, Zygaenidae)

Beside the known existence of cyanoglucosides (linamarin and lotaustralin) and proteins the neurotoxin beta-cyanoalanine has been demonstrated for the first time in the defensive secretions of animals. It is proposed that beta-cyanoalanine is produced by metabolizing cyanide from the cyanoglucosides. The methanolic precipitated protein fraction contains high amounts of aspartic acid, glycine, alanine, leucine and serine, thus being similar to the composition of larval silks in Lepidoptera. The defensive secretion contains 85% water, 8% proteins, 7% cyanoglucosides, 0.3% beta-cyanoalanine and beta-glucosidase while beta-cyanoalanine-synthetase could only be detected in the haemolymph.     

Presence of a trimethylamine: HS-coenzyme M methyltransferase in Methanosarcina barkeri

A trimethylamine:2-mercaptoethanesulfonate (HS-coenzyme M) methyltransferase has been shown to be present in trimethylamine-grown cells but not in methanol-grown cells of Methanosarcina barkeri. The transfer of one methyl group was catalyzed by this enzyme so that dimethylamine and methyl-S-coenzyme M were the products. Enzyme activity required the presence of ATP and preincubation of the protein solution under H₂. Fifty percent of the maximum activity was obtained under N₂ in the presence of NAD(P)H plus dithioerythritol.Abbreviations HS-coenzyme M 2-mercaptoethanesulfonic acid - methyl-S-coenzyme M 2-(methylthio)ethanesulfonic acid - TES N-tris (hydroxymethyl)-methyl-2-aminoethanesulfonic acid - DTE 1,4-dithioerythritol - BrES 2-bromoethanesulfonic acid - DTT 1,4-dithiothreotol