Abstract: Based on the amino acid sequence of prothoracicostatic peptide of the silkworm, Bombyx mori, a group of analogs of Bom-PTSP were synthesized by chemical modifications, such as adding, removing, exchanging amino acid of the peptide. By using silkworms' prothoracic glands in vitro culture and ³H-ecdysteriodradioimmunoassay, the biological activities of those analogs were examined, and their activation features, chemical parameters, and the relationship between structure and function of those peptides were compared and analyzed. It was found the analog 899808 had the same biological function and the similar activity as Bom-PTSP. The analogs 899805 and 899809 partially stimulated ecdysteroidogenesis in a dose dependent manner, while 899803, 899804, 899806 and 899807 had both stimulatory and inhibitory effects on ecdysteroidogenesis, depending on concentration. A possible mechanism of biological activity of Bom-PTSP was discussed.

Key words: Bombyx mori, prothoracicostatic peptide, analog, ecdysteroid, peptide