SLU-PP-332 is not a peptide: it is a synthetic small molecule, an aryl hydrazone with the formula C18H14N2O2 and a molecular weight of 290.32 g/mol (CAS 303760-60-3), that acts as a pan-agonist of the estrogen-related receptors ERRα, ERRβ and ERRγ in vitro. This guide explains why the phrase "SLU-PP-332 peptide" appears so often, what the compound actually is at the level of structure, how it differs from the peptides it is catalogued next to, and how a laboratory classifies and handles it correctly.
Why do people search for "SLU-PP-332 peptide"?
Because of where it is sold, not what it is. Research suppliers that specialise in peptides list SLU-PP-332 in the same catalog as BPC-157, tesamorelin or MOTS-c, and the word "peptide" attaches itself to the product name by association. The compound is studied in the same metabolic and mitochondrial assays as several peptides, which reinforces the habit. Chemically, however, SLU-PP-332 has nothing in common with a peptide, and calling it one in a methods section or a certificate of analysis would be an error.
What is SLU-PP-332 chemically?
SLU-PP-332 is an acylhydrazone built from two aromatic halves: a 4-hydroxybenzoyl group and a 2-naphthyl group, joined through a hydrazone linkage (C=N–NH–C=O). The systematic name is 4-hydroxy-N'-[(E)-naphthalen-2-ylmethylidene]benzohydrazide. There are no amino acids, no amide backbone of the kind that defines a peptide, and no chirality; the single stereochemical descriptor in the name is the (E) geometry of the C=N double bond. The compound was developed in the Burris laboratory at Saint Louis University as a tool ligand for the estrogen-related receptor family, which is where the "SLU-PP" prefix comes from.
| Identifier | SLU-PP-332 |
|---|---|
| Chemical name | 4-hydroxy-N'-[(E)-naphthalen-2-ylmethylidene]benzohydrazide |
| Compound class | Aryl hydrazone (acylhydrazone); small molecule, non-peptide |
| CAS number | 303760-60-3 |
| PubChem CID | 5338394 |
| Molecular formula | C18H14N2O2 |
| Molecular weight | 290.32 g/mol |
| Other codes | ERR pan-agonist 332; SR9861 |
| Target | Estrogen-related receptors ERRα, ERRβ, ERRγ (pan-agonist) |
The identifiers in that table are what belong in a methods section and on a COA. The PubChem CID and CAS number were cross-checked for this article; some older pages cite a different CID, so verify against the formula and molecular weight rather than the number alone.
How does a small molecule differ from a peptide in the lab?
The practical differences matter more than the definitional ones. A peptide such as BPC-157 (1,419.5 g/mol, fifteen residues) is a polar, water-soluble chain that is supplied lyophilized and reconstituted in an aqueous solvent. SLU-PP-332 is a flat, largely hydrophobic aromatic molecule of 290 g/mol with poor water solubility; it is dissolved in DMSO to make a concentrated stock and then diluted into assay medium. Peptides are characterised by HPLC purity plus mass spectrometry of the intact sequence; a small molecule is characterised by HPLC purity plus a mass or NMR spectrum consistent with its structure. The general distinctions are laid out in peptide vs protein vs small molecule; SLU-PP-332 sits firmly in the small-molecule column.
What are the estrogen-related receptors?
ERRα, ERRβ and ERRγ are orphan nuclear receptors. Despite the name, they do not bind estrogen; they were named for sequence similarity to the estrogen receptor. They act as transcription factors that, together with the coactivators PGC-1α and PGC-1β, drive gene programs for mitochondrial biogenesis, oxidative phosphorylation, fatty-acid oxidation and the TCA cycle. Because the receptors are constitutively active in the absence of a natural ligand, synthetic agonists and inverse agonists are the main tools for probing what the pathway does. SLU-PP-332 is one such agonist and, unusually, activates all three isoforms, which is why it is described as a pan-agonist. The existing investigator's guide to SLU-PP-332 covers the receptor biology in more depth.
What does ERR activation look like in a cell-based assay?
The readouts are transcriptional and metabolic. In cultured muscle cells such as C2C12 myotubes, the published work reports induction of ERR target genes, among them those encoding PGC-1α, carnitine palmitoyltransferase and pyruvate dehydrogenase kinase 4, measured by quantitative PCR, together with increased oxygen-consumption rate measured on a plate-based respirometer. Reporter-gene assays in which cells co-express an ERR isoform and an ERR-responsive luciferase construct give concentration–response curves; the reported activity for SLU-PP-332 is in the sub-micromolar range, strongest at ERRα. The assay logic is described in gene-expression assays in vitro and in the dedicated respiration-assay guide for ERR agonists.
How should SLU-PP-332 be referred to in a methods section?
As "SLU-PP-332 (CAS 303760-60-3), a synthetic pan-agonist of ERRα/β/γ", with the supplier, lot number and COA purity, the stock solvent (DMSO) and the final concentration in molarity. Avoid "peptide" entirely. If the catalog listing uses the word, the listing is a sales category, not a chemical classification; the COA and the identifiers above are what define the material. Sourcing and identity checks are covered in sourcing SLU-PP-332 as a research material.
Related research guides
- SLU-PP-332: a novel ERR agonist in in vitro research (investigator's guide)
- SLU-PP-332 solubility and DMSO stock solutions
- SLU-PP-332 vs SLU-PP-915: related ERR-agonist research compounds
- SLU-PP-332 published studies: what the literature shows
- Mitochondrial respiration assays for ERR agonists
- Sourcing SLU-PP-332: COA, purity and identity
Research-use note
All materials discussed are supplied for in vitro laboratory research use only, and are not for human or animal use.
