Novel insulin-releasing peptides in the skin of Phyllomedusa trinitatis frog include 28 amino acid peptide from dermaseptin BIV precursor.
OBJECTIVE
The granular glands of amphibians have long been known to produce many biologically active compounds. The aim of this study was to isolate and characterize insulinotropic peptides from the skin of Phyllomedusa trinitatis frog.


RESULTS
Crude secretions obtained by mild electrical stimulation of the dorsal skin surface were purified by reverse phase HPLC yielding 80 fractions. In acute incubations with glucose-responsive BRIN-BD11 cells, fractions 39-40 (band 1) and fractions 43-46 (band 2) significantly stimulated insulin release by 1.5 to 2.5-fold. Pooled fractions in bands 1 and 2 were rechromatographed to 4 homogeneous peaks, each with insulin-releasing activity. Mass spectrometry analysis was successfully completed for 3 peptides, indicating 2996.4, 3379.9, and 8326.4 Da. The sequence of the 2996.4 Da peptide was determined as ALWKDILKNVGKAAGKAVLNTVTDMVNQ. This 28-amino-acid peptide has 100% homology with the C-terminal of the 75-amino-acid dermaseptin BIV precursor of a family of structurally related antimicrobial peptides in the skin of the Phyllomedusinae subfamily.


CONCLUSIONS
These data demonstrate that the defensive skin secretions of P. trinitatis contain biologically active peptides, which may have mammalian counterparts and merit further investigation as insulin secretagogues.
Marenah
L
L
School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, United Kingdom. l.marenah@ulster.ac.uk
McClean
S
S
Flatt
P R
PR
Orr
D F
DF
Shaw
C
C
Abdel-Wahab
Y H A
YH
D000595:Amino Acid Sequence; D000664:Amphibian Venoms / Q000737:chemistry* / Q000494:pharmacology; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000493:pharmacokinetics*; D001001:Anura / Q000378:metabolism*; D002460:Cell Line / Q000187:drug effects / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification / Q000494:pharmacology; D011498:Protein Precursors / Q000737:chemistry / Q000493:pharmacokinetics*; D051381:Rats; D012867:Skin / Q000737:chemistry*; D013268:Stimulation, Chemical
D000664:Amphibian Venoms; D023181:Antimicrobial Cationic Peptides; D007328:Insulin; D010446:Peptide Fragments; D011498:Protein Precursors