Hyperglycemic activity of the recombinant crustacean hyperglycemic hormone B1 isoform (CHH-B1) of the Pacific white shrimp Litopenaeus vannamei

Crustacean hyperglycemic hormone (CHH) is the most abundant neuropeptide produced by the X-organ/sinus gland (XO/SG) complex in the crustacean eyestalk. CHH plays a principal role in the control of glucose metabolism. The CHH-B1 isoform is produced in the eyestalk of Litopenaeus vannamei by alternative splicing of the chhB gene and its cDNA sequence has revealed that this isoform has a non-amidated C-terminal residue (CHH-like peptide). In this work, a recombinant CHH-B1 (rCHH-B1) with a sequence identical to the native hormone was expressed in the methylotrophic yeast Pichia pastoris X-33 and purified from the culture medium by RP-HPLC. The identity of the purified rCHH-B1 was confirmed by N-terminal sequencing and by using an anti-CHH-B1 polyclonal antibody. An in vivo assay showed that the hyperglycemic effect was dependant of the dosage of rCHH-B1, and the maximal hyperglycemic response was obtained with 250 pmol treatment. These results suggest that the amino acid sequence of the C-terminus and its correct structure are both important for the hyperglycemic activity of naturally occurring non-amidated CHH peptides, such as CHH-B1. CHH-B1 appears to be the first reported CHH-like peptide with significant hyperglycemic activity produced in the sinus gland of a penaeid shrimp.