Submandibular gland peptide-T (SGP-T), a heptapeptide with the sequence of threonine, aspartate, isoleucine, phenylalanine, glutamate, glycine, glycine (TDIFEGG), was isolated from the submandibular glands of rats based on the ability of extracts of these glands to reduce the hypotension induced by bacterial lipopolysaccharide. SGP-T was also found to decrease the severity of the cardiovascular shock provoked by antigen administration to ovalbumin-sensitized rats. An analysis of the structure-activity relationship revealed that three amino acids, phenylalanine, glutamate, glycine (FEG), located in the carboxy terminal of SGP-T were sufficient to inhibit intestinal anaphylaxis in vitro. Interestingly, the D-isomeric form of FEG (feG) did not inhibit anaphylaxis in the in vitro assay. However, both tripeptides, FEG and feG, significantly reduced anaphylactic hypotension and intestinal anaphylaxis in vivo. SGP-T may be a prototype of a family of small peptides that modulate the immune and smooth muscle reactions to severe inflammatory stress. SGP-T preferentially inhibits cardiovascular anaphylaxis, whereas feG exhibits a high degree of selectivity for inhibiting intestinal anaphylaxis in vivo.
Biomedical Reviews 1998; 9: 101-106.
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