Allatoregulatory peptides—molecules with multiple functions

Abstract

Summary There are only a few known neuropeptides and their precursors which are structurally similar to the allatotropin of Manduca sexta, which stimulates the biosynthesis of juvenile hormone in corpora allata in vitro. Allatostatic peptides, on the other hand, which inhibit the biosynthesis of juvenile hormone, are known from a much larger number of insect species. The allatostatins are divided into three types: moth allatostatins, which are characterised by 15 amino acid residues with a pyroglutamate N-terminus and a free carboxy terminus; A- family allatostatins, which are characterised by the pentapeptide sequence Y/FXFGLamide at the C-terminus; and B-family allatostatins, which are characterised by W(X6) Wamide. For each type of allatostatin, precursors are known and these always encode multiple peptides with the exception of the moth type. To date, receptors for allatostatins have only been identified for the A-allatostatins. Whereas allatostatic effects are demonstrated for A-ASTs in crickets and cockroaches, for B-ASTs in crickets and for moth AST in moths, multiple other functions for each type of AST have also been established; for example, inhibition of myotropic activity, inhibition of heart beat, inhibition of vitellogenin release, inhibition of the production of ecdysteroids by prothoracic glands and ovaries in vitro and stimulation of the activity of carbohydrases in vitro.