Molecule guides
What Is Liraglutide? The First Acylated GLP-1 Analogue: Structure, Mechanism and Research
Liraglutide is GLP-1(7-37) with one substitution and a C16 palmitate. Here is why its hours-long exposure makes it a distinct research tool, and how to handle and verify it.
Liraglutide is a 31-amino-acid GLP-1 receptor agonist bearing a palmitoyl chain, and it is the compound that introduced the lipidation approach now standard across the incretin class. It deviates from native GLP-1 at just one residue and carries a C16 palmitic acid, which stretches its circulating lifetime from minutes to hours — long enough to be practical, yet short enough to make it a truly different experimental tool from the multi-day analogues that came after it. Our research-grade liraglutide is supplied as lyophilized powder in sealed vials, for laboratory use only.
Clinical data in humans relate to the approved medicinal products based on this molecule. Those data describe a regulated medicine, not the reference material offered here.
Liraglutide defined
Liraglutide was the first-generation answer to the problem that renders native GLP-1 impractical as a research tool: a plasma half-life of just one to two minutes, caused by dipeptidyl peptidase-4 cleavage and fast renal elimination. The design leaves the GLP-1(7-37) sequence almost untouched — only Lys34 is swapped for arginine — and attaches a C16 palmitic acid to Lys26 via a glutamic acid spacer. The palmitate does two things simultaneously: it binds albumin reversibly, protecting the peptide from clearance, and it drives self-association into heptamers in solution and at the depot site, further slowing release.
This close resemblance to native GLP-1 is why liraglutide is still valuable. When an experiment calls for a GLP-1 receptor agonist whose sequence is as near to the endogenous hormone as stability permits, liraglutide is a better fit than semaglutide, which adds a non-proteinogenic Aib substitution and a longer diacid.
Design and structure
- Sequence. GLP-1(7-37), 31 residues, with one substitution: Lys34 to Arg.
- Lipidation. A C16 palmitic acid on Lys26 through a gamma-glutamyl spacer — a shorter mono-acid lipid than the C18 and C20 fatty diacids adopted by later analogues.
- No Aib at position 8. Liraglutide keeps the native alanine at position 8 and is therefore still a DPP-4 substrate. Its longer duration comes from albumin binding and self-association rather than from protease resistance — the most important structural fact to know about it.
- Identifiers. CAS 204656-20-2, formula C172H265N43O51, molecular weight 3751.20 Da — the lightest acylated GLP-1 analogue in our range.
Mechanism of action
Its receptor pharmacology is standard for the class. Liraglutide binds the GLP-1 receptor, a class B GPCR, stabilises its active state and drives Gs-mediated cAMP production with downstream PKA and Epac2 signalling. In islet preparations this enhances insulin secretion in a glucose-dependent fashion. Receptors in the area postrema, nucleus tractus solitarius, arcuate nucleus and on vagal afferent fibres are implicated in the reduced food intake and delayed gastric emptying described in rodent studies.
Liraglutide differs from later analogues not at the receptor but in its exposure profile. A duration of hours creates peaks and troughs, whereas a multi-day analogue approaches steady-state exposure. Even with an identical receptor, these are separate pharmacological experiments, and several published findings on receptor desensitisation and tachyphylaxis in the GLP-1 field hinge on which exposure pattern was applied. If your question concerns intermittent versus continuous receptor occupancy, that difference is the experiment itself, not a nuisance variable.
Research applications
- Receptor and cell-based studies. cAMP accumulation, binding, beta-arrestin recruitment and receptor internalisation assays in cells expressing the human GLP-1 receptor. Liraglutide is a standard reference agonist in this literature, and most newer molecules are profiled against it.
- Biophysical studies. Work on self-association and heptamer formation, albumin binding and formulation stability — an unusually rich strand for liraglutide, because its self-association governs its kinetics.
- Rodent studies. Feeding behaviour, gastric transit, islet morphology and beta-cell mass, mapping of neuronal activation, and models of hepatic steatosis and neuroinflammation.
- Clinical trials of the approved medicines. Randomised programmes in type 2 diabetes and weight management, as well as a published cardiovascular outcomes trial. These evaluated prescription medicines under medical supervision and say nothing about research-grade powder.
For the broader picture, see the GLP-1 and incretin pathway hub.
Liraglutide also holds a particular historical position that affects how the literature should be read. As the first acylated GLP-1 analogue to be studied in depth, it was used to establish much of the foundational GLP-1 receptor pharmacology — internalisation kinetics, recycling, the link between cAMP output and insulin release in isolated islets. Newer molecules are commonly benchmarked against liraglutide instead of native GLP-1, so when reproducing or extending a published comparison, having the same reference agonist on your bench eliminates a whole category of cross-study discrepancies.
Available formats and vial sizes
Vial sizes and prices are listed on the liraglutide product page, part of the GLP-1 and incretin peptides collection.
Reconstitution and storage at the bench
The calculation is routine: dissolving a 5 mg vial in 2 mL of bacteriostatic water gives 2.5 mg/mL (2,500 mcg/mL), so 0.1 mL of that solution holds 250 mcg of peptide. One handling point is peculiar to liraglutide. Its self-association depends on pH — it dissolves best under mildly alkaline conditions and worst near its isoelectric point, where it may precipitate. A cloudy preparation usually reflects buffer pH rather than degradation, and shaking hard to force it back into solution does more damage than correcting the buffer would.
Keep sealed lyophilized powder at minus 20 degrees Celsius, away from light and moisture; store reconstituted solution at 2 to 8 degrees Celsius and use it within the study period. Aliquot at reconstitution rather than freezing and thawing a shared stock repeatedly. See our reconstitution guide and the note on pH and solubility.
A further practical point concerns self-association. The heptamer equilibrium shifts with concentration, so a concentrated stock and a dilute working solution contain different mixtures of species: at assay concentrations the peptide is mostly monomeric, while in concentrated stock a large share is associated. This matters when a protocol involves making a stock far above the working range and keeping it, because the association state during storage differs from that at the point of use, and re-equilibration takes time. Allowing sufficient equilibration after dilution, instead of diluting immediately before reading a plate, eliminates a genuine source of variability.
Purity and reading the certificate of analysis
A liraglutide certificate should include an HPLC chromatogram with main-peak area percentage, a mass-spectrometric identity result compared with the theoretical 3751.20 Da, net peptide content, lot number and date of analysis. For an acylated peptide made this way, two impurity classes deserve attention: incompletely acylated peptide, which lacks the palmitate and so has shorter duration and altered kinetics yet may not stand out in a headline purity figure; and des-amino or deletion sequences arising from incomplete coupling. A chromatogram showing resolved shoulders is more informative than a single percentage. Read how to read a COA, and check that the lot matches your vial.
Lastly, the shorter half-life can be an advantage at the bench rather than a drawback. A compound that clears within hours lets you perform a washout and re-establish baseline within one experiment, something a multi-day analogue cannot offer without adding a week to the study. For crossover designs, repeated-measures protocols and any question about how receptor responsiveness recovers after agonist exposure, this is precisely why liraglutide should be chosen deliberately instead of defaulting to the most potent long-acting option.
Regulatory position
As a pharmaceutical, liraglutide is an approved prescription medicine in the United States, the EU and many other jurisdictions, and generic versions have launched in several markets since the originator patents expired. Research-grade liraglutide belongs to a completely different category: it is a chemical reference material for laboratory research only, not for human use. Patent expiry does not affect that distinction.
Related compounds and comparisons
The natural comparison is with its longer-acting successor built on the same backbone, discussed in liraglutide vs semaglutide; the semaglutide product page lists that alternative. For multi-receptor molecules, see retatrutide, and for the older exendin-based agonist, exenatide.
Questions
In what ways does liraglutide differ from native GLP-1?
It differs by a single amino acid and a single lipid. Arginine replaces Lys34 so that acylation occurs at only one site, and a C16 palmitic acid is attached to Lys26 through a glutamic acid spacer. The remainder of GLP-1(7-37) is unchanged, making liraglutide the closest practical analogue of the native hormone in this class.
Does liraglutide resist DPP-4 cleavage?
No — and this is its defining structural feature. It keeps the native alanine at position 8, so DPP-4 can still cleave it. Its longer duration comes from albumin binding and heptamer self-association rather than protease resistance, unlike semaglutide, which adds an Aib8 substitution to block cleavage entirely.
Why do researchers still use liraglutide when longer-acting analogues are available?
Because duration is itself an experimental variable, not merely a convenience. Liraglutide gives peak-and-trough receptor occupancy over hours, whereas multi-day analogues approximate steady state. Questions about receptor desensitisation, tachyphylaxis and intermittent versus continuous signalling can only be answered with the shorter-acting tool.
What is liraglutide's molecular weight?
It is 3751.20 Da, with the formula C172H265N43O51 and CAS 204656-20-2. It is the lightest acylated GLP-1 analogue in this range, reflecting its shorter C16 palmitate compared with the C18 and C20 fatty diacids of later molecules.
Why can a liraglutide solution appear cloudy?
Usually because of pH rather than degradation. Liraglutide self-associates and is least soluble close to its isoelectric point and most soluble in mildly alkaline conditions. Check and correct the buffer instead of shaking the vial, as mechanical agitation encourages irreversible aggregation of acylated peptides.
Which impurities matter on a liraglutide certificate?
Incompletely acylated peptide is the key one: without the palmitate it has different kinetics, yet it may not show up in a headline purity figure. Deletion and des-amino sequences from incomplete coupling also matter. A chromatogram with resolved shoulders tells you more than a single percentage.
Does the availability of generic liraglutide change its status for research use?
No. Generic entry applies to approved pharmaceutical products that are manufactured and dispensed on prescription. Research-grade liraglutide remains a laboratory reference chemical whatever the patent status of the medicine.