PE 22-28

PE 22-28 is a synthetic heptapeptide corresponding to residues 22 to 28 of the sortilin propeptide. It is not a fragment of spexin; see the nomenclature note.

CORRECTION, 2026-09-13. This entry previously described PE 22-28 as residues 22 to 28 of spexin and carried the alias Spexin (22-28). That was wrong, and it is wrong for a reason that can be checked without any source: mature spexin is fourteen residues long, so residues 22 to 28 of it do not exist, and the sequence Gly-Val-Ser-Trp-Gly-Leu-Arg appears nowhere within spexin's sequence Asn-Trp-Thr-Pro-Gln-Ala-Met-Leu-Tyr-Leu-Lys-Gly-Ala-Gln. The PE in PE 22-28 denotes the sortilin propeptide, not a peptide. Gly-Val-Ser-Trp-Gly-Leu-Arg is residues 22 to 28 of that propeptide, and the same seven residues form the C-terminal end of the longer sortilin-propeptide-derived peptide spadin. PE 22-28 has no sequence relationship to spexin at all. The two references currently cited on this page concern spexin and are retained only until this entry receives its own evidence; they do not characterize this molecule and should not be read as doing so.

Declared aliases and development codes: PE(22-28), Sortilin propeptide (22-28).

The seven residues of PE 22-28 also form the C-terminal end of spadin, a longer peptide derived from the same sortilin propeptide. No verified source examined for THIS entry characterizes the heptapeptide independently, and its mechanism field is deliberately empty rather than populated from work on longer relatives. The fragment contains a single tryptophan residue, the only aromatic residue in the sequence.