Isolation of crustacean hyperglycemic hormone-family peptides with vitellogenesis-inhibiting activity from the shiba shrimp Metapenaeus joyneri

Vitellogenesis-inhibiting hormone (VIH) in Crustacea belongs to the crustacean hyperglycemic hormone (CHH)-family. In order to characterize multiple VIH molecules in the shiba shrimp Metapenaeus joyneri, four CHH-family peptides designated as Mej-SGP-I, -II, -III, and -IV were purified by reversed-phase HPLC and identified by N-terminal amino acid sequencing. The vitellogenesis-inhibiting activities of these peptides were examined using ex vivo incubation of ovarian fragments of the kuruma prawn Marsupenaeus japonicus. All of the four peptides significantly reduced vitellogenin mRNA levels in the ovarian fragments. Among them, the inhibitory activity of Mej-SGP-III which was the most abundant CHH-family peptide in the sinus gland was apparent. Therefore, a cDNA encoding the Mej-SGP-III precursor was cloned by RT-PCR coupled with 5′- and 3′-RACE. The mature Mej-SGP-III was found to consist of 72 amino acid residues containing six conserved cysteine residues and possess an amidated C-terminus. The mature Mej-SGP-III showed the highest sequence identity to Pej-SGP-V (one of six CHH/VIHs in M. japonicus) and Liv-SGP-G (one of six VIHs in Litopenaeus vannamei). These results indicate that Mej-SGP-III is one of the hormones regulating vitellogenesis in M. joyneri.