Isolation and some characterization of the prothoracicotropic hormone from Bombyx mori

The prothoracicotropic hormone (PTTH) was isolated from adult heads of Bombyx mori. Fifty micrograms of pure PTTH was obtained from 648,000 heads through a 15-step purification procedure with a 2 X 10(6)-fold purification and an 8% recovery. Chemical analyses of this PTTH have shown that it is a single-chain peptide consisting of 40-43 amino acid residues (MW, 4330-4740), the N-terminus of which is glycine. As little as 0.1 ng of PTTH elicited adult development in a debrained pupa of Samia cynthia ricini. Five picograms of PTTH directly stimulated the prothoracic glands in vitro so as to enhance ecdysone release. The hemolymph ecdysteroids of brainless Samia pupae that were developed by PTTH injection increased with essentially the same pattern as in developing normal pupae.