Three questions hide inside the word glutathione. The first is chemical identity: which residues and which bonds make up the molecule. The second is oxidation state: whether a description means the reduced thiol form, GSH, or the disulfide, GSSG, a different compound with its own formula and mass. The third is supplied format: powder, liquid, or a formulation word such as liposomal, none of which answers the first two. This page separates the three and shows how to read a chemical record, a reaction equation, and an analytical report without letting one stand in for another.
It is a chemistry and documentation reference, not a guide to the material. The existing glutathione guide carries the catalog description and the shared handling blocks, and the research guide index lists the other references. Nothing here covers biological roles, dietary sources, or how to prepare, select, or store any form of the compound.
What does the name glutathione identify?
Glutathione is a tripeptide, a chain of three amino acid residues. The ChEBI record for the neutral entity names them as glutamic acid, cysteine, and glycine, and describes the glutamic acid unit as connected through its side chain to cysteinylglycine, the dipeptide formed by the other two. The record's systematic name, L-gamma-glutamyl-L-cysteinylglycine, packs that into one string: residues read from the glutamyl end to the glycine end, an L descriptor on each chiral residue and none on glycine, and the prefix gamma marking the unusual connection point.
Glutathione is a tripeptide made of three amino acid residues: glutamic acid, cysteine, and glycine. The ChEBI record names it L-gamma-glutamyl-L-cysteinylglycine, because the glutamic acid residue is joined through its side-chain carboxyl group rather than its alpha carboxyl group, a linkage the IUPAC-IUB peptide nomenclature uses as its standard gamma-linked example. The neutral reference entity has the formula C10H17N3O6S and carries a free thiol on the cysteine residue. This describes structure only.
The record also lists the synonyms GSH and glutathione-SH. The SH points to the cysteine side chain, which ends in a sulfur atom bonded to a hydrogen atom, a thiol group. ChEBI classifies the entity as a thiol and a tripeptide: structural classes that say nothing about what the molecule does.
Two identifiers travel with the record and are easy to over-read. The formula C10H17N3O6S with net charge zero describes the neutral molecule; the record separately links glutathionate(1-), the conjugate base formed when one proton is lost. The CAS registry number 70-18-8 is a cross-reference for locating the same substance in other databases. Neither describes a physical sample: a formula on a label names the entity the writer intended, not what is in the container, and a CAS number is an index key, not an assay. The site's glutathione product entry is where a material-specific description would appear.
Why does the gamma linkage belong in glutathione's chemical description?
An ordinary peptide bond joins the carboxyl group on one residue's alpha carbon to the amino group on the next residue's alpha carbon. Glutamic acid has two carboxyl groups: one on the alpha carbon and one at the end of its side chain, called the gamma carboxyl because it hangs from the gamma carbon, the third carbon counting away from the alpha carboxyl carbon. In glutathione the side-chain one forms the amide bond, and the glutamyl residue's alpha carboxyl group stays free.
The IUPAC-IUB peptide nomenclature recommendations use glutathione as their example of exactly this situation. Its descriptive name, gamma-glutamylcysteinylglycine, carries the gamma so that a reader knows the glutamyl residue is bonded through its side chain.
Glutathione, L-gamma-glutamyl-L-cysteinylglycine (teaching sketch, neutral form) HOOC-CH(NH2)-CH2-CH2-C(=O)-NH-CH(CH2-SH)-C(=O)-NH-CH2-COOH [ glutamyl residue ] [ cysteinyl residue ] [ glycine ] free alpha carboxyl: HOOC at the far left free alpha amino: NH2 on the glutamyl alpha carbon gamma linkage: first C(=O)-NH, from the side-chain carboxyl thiol group: CH2-SH on the cysteine side chain alpha linkage: second C(=O)-NH, an ordinary peptide bond gamma-Glu-Cys-Gly linkage marked: glutathione Glu-Cys-Gly no marker: read as the alpha-linked chain
In the standard notation a plain hyphen between residue symbols is read as the ordinary alpha linkage unless an annotation says otherwise, so the bare string Glu-Cys-Gly describes the alpha-linked tripeptide, not glutathione. The two chains hold the same residues in the same order, and each amide bond forms with the loss of the same atoms of water whichever carboxyl group supplies it, so both share the formula C10H17N3O6S. The formula alone cannot say which is meant; connectivity has to be stated by a name with the gamma prefix, a structure drawing, or an explicit annotation. A document that gives only a formula and a residue list has left the linkage not stated.
How do GSH and GSSG differ as chemical entities?
Glutathione oxidation, as a chemical topic, is about the thiol group. When two glutathione molecules each lose the hydrogen on their sulfur atom and the two sulfur atoms bond to each other, the product is one larger molecule, glutathione disulfide, which has its own ChEBI record. The displayed structure shows two glutathione-derived units joined through a sulfur-sulfur connection; the synonyms are GSSG, oxidised glutathione, and oxidized glutathione; and the neutral entity has the formula C20H32N6O12S2, net charge zero, and its own registry cross-reference, 27025-41-8.
GSH and GSSG are two different chemical entities with separate database records. GSH, reduced glutathione, is one tripeptide with a free thiol group, formula C10H17N3O6S. GSSG, glutathione disulfide, is two glutathione-derived units joined through a sulfur-sulfur bond, formula C20H32N6O12S2. The glutathione-disulfide reductase equation in the IUBMB record relates two GSH molecules and NADP+ to one GSSG, NADPH, and H+, so a report must state which entity it measured.
GSH, one molecule GSH, one molecule
gamma-Glu-Cys-Gly gamma-Glu-Cys-Gly
| |
CH2 CH2
| |
S-H H-S
two separate thiol groups
GSSG, glutathione disulfide, one molecule
gamma-Glu-Cys-Gly
|
CH2
|
S
| sulfur-sulfur bond
S
|
CH2
|
gamma-Glu-Cys-GlyThe IUBMB entry for glutathione-disulfide reductase adds a nomenclature comment preferring glutathione disulfide over the phrase oxidized glutathione, which it calls ambiguous: the vaguer phrase could mean glutathione altered in some unspecified way, while glutathione disulfide names one compound with one specific bond.
The same entry, EC 1.8.1.7, writes out the reaction connecting the two entities: two glutathione molecules plus NADP+ relate to one glutathione disulfide plus NADPH plus H+. Three reading rules follow. The count is two to one, so a total that counts glutathione units must say whether a GSSG molecule counts once or twice. The cofactor pair is NADP+ and NADPH, not NAD+ and NADH, which are different compounds. And the equation is a chemical relationship: it states no rate, proportion, or result for any sample.
What is glutathione's molecular weight, and which entity is being weighed?
Searches for glutathione molecular weight or glutathione mw usually want one number. A reference record gives two, and they answer different questions. The table matches the two ChEBI entries field for field.
| Property | Glutathione (GSH) | Glutathione disulfide (GSSG) |
|---|---|---|
| ChEBI identifier | CHEBI:16856 | CHEBI:17858 |
| Record name | L-gamma-glutamyl-L-cysteinylglycine | Glutathione disulfide |
| Listed synonyms | GSH, glutathione-SH | GSSG, oxidised glutathione, oxidized glutathione |
| Neutral formula | C10H17N3O6S | C20H32N6O12S2 |
| Net charge | 0 | 0 |
| Average mass | 307.328 | 612.640 |
| Monoisotopic mass | 307.08381 | 612.15196 |
| Sulfur connectivity | One thiol group, S-H | One sulfur-sulfur bond between two units |
| Linked conjugate base | glutathionate(1-) | glutathione disulfide(2-) |
| CAS cross-reference | 70-18-8 | 27025-41-8 |
Average mass and monoisotopic mass are two calculations on the same neutral formula. PubChem's computed-property record for glutathione (CID 124886) defines molecular weight as the sum of the mass of each constituent atom multiplied by the number of atoms of that element in the formula, reported in daltons relative to carbon-12, and defines monoisotopic mass as the same sum taken with the rest mass of the principal, most abundant isotope of each element instead of the isotopic average. That is why the monoisotopic figure is lower and carries more decimal places. The PubChem record lists 307.33 and 307.08380644 for the same neutral formula, consistent with the ChEBI values quoted above. This page uses those definitions as recorded and does not derive one figure from the other.
The entity being weighed matters as much as the arithmetic. Both masses belong to the neutral molecule; the linked conjugate bases, glutathionate(1-) and glutathione disulfide(2-), are different entities with different formulas and masses. A mass spectrometer measures ions, not neutral molecules, and an ion has gained or lost charged particles, so the mass-to-charge value an instrument reports is not simply the neutral database mass. Reading an instrument value against a reference record requires knowing which ion the method formed; this page calculates no such value.
How is glutathione assembled in the documented enzyme pathway?
Glutathione pathway and biosynthesis of glutathione are chemistry questions with a compact answer: two enzyme-catalyzed steps, each with its own Enzyme Commission entry in the IUBMB nomenclature.
The IUBMB enzyme records describe glutathione biosynthesis as two separately catalyzed joining steps. Glutamate-cysteine ligase, EC 6.3.2.2, joins L-glutamate and L-cysteine into gamma-L-glutamyl-L-cysteine, converting ATP to ADP and phosphate. Glutathione synthase, EC 6.3.2.3, then adds glycine to that intermediate to form glutathione, again with ATP to ADP and phosphate. These equations describe chemical relationships in a biological pathway. They say nothing about how any supplied research material was produced.
step 1 glutamate-cysteine ligase, EC 6.3.2.2
also listed as gamma-glutamylcysteine synthetase
L-glutamate + L-cysteine + ATP
|
v
gamma-L-glutamyl-L-cysteine + ADP + phosphate
step 2 glutathione synthase, EC 6.3.2.3
also listed as glutathione synthetase
gamma-L-glutamyl-L-cysteine + glycine + ATP
|
v
glutathione + ADP + phosphateRead the diagram as bookkeeping. In step one the ligase joins L-glutamate and L-cysteine, and the product named in the record is gamma-L-glutamyl-L-cysteine: the pathway builds the unusual side-chain bond first. ATP appears as a reactant and ADP plus phosphate as products, carried through without interpretation. In step two, glutathione synthase adds glycine to that dipeptide intermediate, again with ATP to ADP and phosphate, and the product is glutathione.
Names cause trouble here. The alternative name gamma-glutamylcysteine synthetase belongs to the first enzyme, which makes the intermediate, not to the final tripeptide. The second enzyme's accepted name is glutathione synthase, with glutathione synthetase as a listed synonym; both name the enzyme, neither the compound. When a document mentions a synthetase, check whether it means the enzyme, the intermediate, or the tripeptide.
The largest misreading is about origin. A biosynthesis pathway describes how living systems build a molecule. It says nothing about how a particular research material was made, where, or by what process, and an enzyme record proves nothing about any lot. The pathway is here because it explains the gamma linkage and the residue order; it has no place on a certificate.
How is oxidation state different from powder, liquid, or formulation wording?
The phrase glutathione liquid form illustrates the confusion this page exists to resolve. Liquid is a physical description: the material was fluid when described. It does not say whether the glutathione present is GSH, GSSG, or a mixture, because oxidation state is a property of molecules and physical form is a property of a bulk material. The same holds for powder, solution, and every formulation adjective. The table separates five dimensions that documentation often collapses into one.
| Dimension | Example terms | Question it answers | What it leaves open |
|---|---|---|---|
| Oxidation state | GSH, reduced glutathione; GSSG, glutathione disulfide | Free thiol or sulfur-sulfur bond | Ionic state, physical form, proportion, and how it was measured |
| Ionic state | Neutral molecule; glutathionate(1-); glutathione disulfide(2-); a named salt | Which protonation or salt form is meant | Physical form and composition |
| Physical form | Powder, lyophilized solid, liquid, solution | The bulk state when described | Which entity is present, in what proportion and ionic state |
| Formulation term | Liposomal, buffered, similar descriptors | That the writer claims a formulation approach | Every structural and compositional fact; the word alone carries no verified detail |
| Analytical derivative | N-ethylmaleimide adduct of GSH, as in the cited method | What the instrument detected in place of the native molecule | The native composition before derivatization, unless the method says how it was preserved |
Two rows carry a caution. Liposomal appears in searches for pure liposomal glutathione; here it is only an example of a formulation descriptor, because no primary source on liposome structure was read for this brief. The word pure attached to it does not state a GSH/GSSG proportion: pure describes the share of an intended entity relative to everything else and does not say which oxidation state was intended. An analytical derivative is a laboratory artifact created for measurement, so a report quoting a derivative value is reporting on the derivative; the link back to the native molecule belongs to the method.
What does a GSH/GSSG analytical report need to explain?
A report that gives a GSH value, a GSSG value, or a ratio has made a chain of decisions before the number appears, and a reader needs each link stated. The clearest bounded example available here is the 2020 method paper by Sun and colleagues indexed in PubMed; its abstract and figure captions were read for this brief, and the full text was not retrieved. It is a worked example of a complete method description, not a general standard.
GSH/GSSG results are hard to compare because each number depends on choices before detection. The method study by Sun and colleagues shows why: GSH can autooxidize during sample preparation, so they derivatized it with N-ethylmaleimide in cultured cells, separated the sample chromatographically, detected the GSH derivative by UV and GSSG by QTOF mass spectrometry, and calibrated each channel differently. Two reports that differ in analyte definition, matrix, preservation, detection channel, or calibration describe different measurements.
The abstract describes the decisions in order. The target is two analytes, GSH and GSSG, measured through different channels. The matrix is cultured cells, and a method described in one matrix carries no promise about another. The problem addressed is autooxidation: GSH can convert to GSSG during preparation, lowering the GSH reading and raising the GSSG reading before the instrument sees the sample. The answer is derivatization: N-ethylmaleimide reacts with the thiol group of GSH to lock it into a stable adduct, and that adduct, not native GSH, is what the instrument measures.
Detection follows separation. After chromatography, the GSH derivative is read by UV absorbance and GSSG by quadrupole time-of-flight mass spectrometry, QTOF-MS. Two channels mean two calibrations, and the Figure 2 caption distinguishes them: one for the derivative, and a ratio-based calibration for GSSG against an isotope-labeled internal standard, a heavier isotopic version of GSSG added so the analyte is measured relative to it. The abstract also reports calibration range, detection and quantification limits, recovery, and repeatability separately; none is interchangeable with molecular identity, and none describes any supplied product.
One caption carries its own lesson. Figure 1 describes two peaks for the GSH derivative and identifies them as diastereomers: the reagent can attach in two spatial arrangements that separate on the column. Counting peaks and concluding there is an impurity misreads the chromatogram, because the method itself produces two peaks from one analyte. For the general structure of a certificate, the guide to reading a certificate of analysis is the owner; this section covers only the redox-specific questions.
How do you compare two glutathione descriptions without inventing missing facts?
Comparison is where invented facts creep in. Two descriptions of glutathione rarely state the same fields, and the temptation is to fill gaps from memory. The worksheet below is deliberately empty; every field accepts the value not supplied, and writing that phrase is the correct result whenever a document is silent.
| Field | What to copy from the document | Teaching example entry |
|---|---|---|
| Analyte | Exact entity named: GSH, GSSG, total glutathione, or a derivative | not supplied in this example |
| Matrix | Sample type measured | not supplied in this example |
| Reference form | Database entity or reference standard compared against | not supplied in this example |
| Unit | Mass, amount, concentration, or ratio, as written | not supplied in this example |
| Derivatization | Reagent named, or an explicit none | not supplied in this example |
| Measurement channel | Detector and separation, such as UV or QTOF-MS after chromatography | not supplied in this example |
| Calibration | Type, range, and any internal standard | not supplied in this example |
| Limits | Detection and quantification limits as reported | not supplied in this example |
| Unresolved fields | Every field left as not supplied | all fields, in this empty example |
Two checks make a comparison valid. The matched-entity check asks whether both documents name the same analyte; a GSH value and a total-glutathione value are not the same measurement even when the units agree. The matched-unit check asks whether the units are the same kind of quantity; a mass and a concentration cannot be compared without volume information that may not be stated. If either fails, the honest result is not comparable. Not stated and not detected are also different findings: not stated means the document is silent, while not detected means the method looked and found nothing above its detection limit, which is only meaningful with that limit attached. Recording not detected for a field the document never mentions fabricates a result.
| Entity | Neutral formula from the record | Hydrogen atoms | Comment |
|---|---|---|---|
| Two GSH molecules | 2 x C10H17N3O6S = C20H34N6O12S2 | 34 | Sum of two reference formulas |
| One GSSG molecule | C20H32N6O12S2 | 32 | Reference formula from the disulfide record |
| Difference | Two hydrogen atoms | 2 | Consistent with two thiol hydrogens absent once the sulfur-sulfur bond exists |
A worked example, with placeholders. A first description reads: glutathione, C10H17N3O6S, CAS 70-18-8, lot <supplier-lot>. A second reads: glutathione, liquid, GSH/GSSG ratio reported, lot <supplier-lot>. The first names the reduced entity by formula and registry number, matching the ChEBI record, and says nothing about measured composition, so every worksheet field after reference form is not supplied. The second claims a measurement without naming analyte, matrix, derivatization, channel, calibration, or limits, so the ratio cannot be placed on the worksheet at all. Neither is wrong on its face, but they are not comparable. Where such records are kept for materials on this site is answered at quality documentation; whether any record exists, is current, or is adequate is not something this page can state.
Frequently asked questions
Are reduced glutathione and glutathione disulfide the same compound?
No. Reduced glutathione, GSH, is a single tripeptide with a free thiol group on its cysteine residue, recorded in ChEBI with the neutral formula C10H17N3O6S and the registry cross-reference 70-18-8. Glutathione disulfide, GSSG, is one molecule made of two glutathione-derived units bonded through their sulfur atoms, with the neutral formula C20H32N6O12S2 and a different registry number, 27025-41-8. They have different masses, structures, and database records. A document that says glutathione without naming the form has named a family, and the oxidation state should be recorded as not stated.
Why do a reference entry's average mass and monoisotopic mass differ?
They are two calculations performed on the same formula. The ChEBI glutathione record lists an average mass of 307.328 and a monoisotopic mass of 307.08381; the disulfide record lists 612.640 and 612.15196. PubChem's computed-property record for glutathione defines molecular weight as the sum of each constituent atom's mass multiplied by its count in the formula, using isotopic average masses, and defines monoisotopic mass as the same sum using the rest mass of the most abundant isotope of each element, which is why the monoisotopic figure is lower. Both belong to the neutral molecule with zero charge. Both figures are quoted from the records as listed, and neither is derived from the other.
Does liquid or liposomal wording specify the GSH/GSSG composition?
No. Liquid describes the physical state of a bulk material, and liposomal describes a formulation approach the writer is claiming. Neither word says whether the glutathione present is the reduced thiol form, the disulfide, or a mixture, and neither states a proportion. Oxidation state is a property of molecules and can only be established by an analytical record that names its analytes, matrix, preservation step, detection channel, and calibration. No claim is made about what format any supplied glutathione takes; a reader who needs the composition should ask for the analytical record.
Why does sample preparation matter when reading a GSH/GSSG report?
Because the reduced form can change into the disulfide before measurement. The 2020 method study by Sun and colleagues addresses GSH autooxidation during sample preparation in cultured cells by reacting the thiol with N-ethylmaleimide, so the instrument detects a stable derivative rather than native GSH. Without a preservation step of that kind, part of the GSH reading may have become GSSG on the bench, shifting both numbers and any ratio between them. A report that omits its preservation details leaves a reader unable to tell whether the values reflect the sample as collected or as it drifted.
Does a biosynthesis pathway establish where a research product was manufactured?
No. The IUBMB records for glutamate-cysteine ligase, EC 6.3.2.2, and glutathione synthase, EC 6.3.2.3, describe how living systems assemble glutathione in two enzyme-catalyzed steps. They are chemical relationships in a biological pathway and contain no information about the process, facility, or country behind any supplied material, so citing them on a product document would not support an origin statement. Manufacturing origin is a separate evidence question answered by production and supply records, none of which are among the cited chemistry sources.
Sources and scope notes
Chemical identity, names, formulas, masses, synonyms, conjugate-base links, and registry cross-references come from the ChEBI records for glutathione, last modified September 11, 2023, and glutathione disulfide, last modified February 22, 2017. Enzyme names and equations come from the IUBMB entries for EC 6.3.2.2, EC 6.3.2.3, and EC 1.8.1.7, and the gamma-linkage example from the IUPAC-IUB 1983 peptide nomenclature recommendations, all read on September 20, 2026, Pacific time. Database records are reference identities, not certificates for any material, and a neutral reference formula is not a specification for every salt, hydrate, or ionic form.
The analytical discussion rests on the PubMed abstract and figure captions of Sun and colleagues, 2020, DOI 10.3390/metabo10070292. The full text and supplementary material were not retrieved, so no experimental conditions, concentrations, or timings appear here, and the study's validity extends only to its reported method and cell-culture matrix. It is not a Glow assay result.
Nothing on this page inspects, infers, or states the formulation, physical form, GSH/GSSG composition, origin, or lot measurements of any supplied material; those remain unknown here. Liposome chemistry and total-glutathione formula conventions were not sourced for this brief.
- ChEBI, CHEBI:16856, glutathione: identity, names, formula, masses, and ontology links Last modified September 11, 2023. Read September 20, 2026.
- ChEBI, CHEBI:17858, glutathione disulfide: identity, formula, masses, structure, and synonyms Last modified February 22, 2017. Read September 20, 2026.
- IUBMB Enzyme Nomenclature, EC 6.3.2.2, glutamate-cysteine ligase Created 1961. Read September 20, 2026.
- IUBMB Enzyme Nomenclature, EC 6.3.2.3, glutathione synthase Created 1961. Read September 20, 2026.
- IUBMB Enzyme Nomenclature, EC 1.8.1.7, glutathione-disulfide reductase Created 1961, modified 1989, transferred 2002. Read September 20, 2026.
- Sun and colleagues, 2020, PubMed 32709039, DOI 10.3390/metabo10070292: GSH and GSSG measurement with N-ethylmaleimide derivatization Abstract and figure captions read September 20, 2026. Full text not retrieved.
- IUPAC-IUB JCBN, Nomenclature and Symbolism for Amino Acids and Peptides (Recommendations 1983), sections 3AA-11 to 3AA-13 Hosted by Queen Mary University of London. Read September 20, 2026.
- PubChem (NCBI/NLM), glutathione CID 124886, Computed Properties record: molecular weight and monoisotopic mass definitions and values (307.33 and 307.08380644) Official PUG View record read September 21, 2026; the human-readable page is https://pubchem.ncbi.nlm.nih.gov/compound/124886.