Glycyl-L-leucine
- Название продукта: Glycyl-L-leucine
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- Glycyl-L-leucine is typically used in formulations when pH and temperature must be controlled within specific ranges.
| Код ТН ВЭД | 870179 |
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Does Peptide-Bound Leucine Alter Proteolytic Stability in Topical Dermatological Formulations?
The use of Glycyl-L-leucine in leave-on dermatological preparations targets controlled leucine release to the stratum corneum while reducing the osmotic load associated with free amino acid addition. Published formulation work indicates that the dipeptide is incorporated into oil-in-water emulsion systems at 0.5–2.0% w/w where keratinocyte-associated leucine aminopeptidase activity on corneocyte surfaces cleaves the peptide bond at a measured rate of 0.1–0.3 nmol leucine/cm²/h from ex vivo porcine skin under occlusive conditions. Rheological stability of the emulsion remains acceptable when Glycyl-L-leucine is pre-dissolved in the water phase at 25–30°C before carbomer neutralization with triethanolamine; direct powder addition during the cooling phase produces visible agglomerates above 1.5% w/w due to localized ionic strength gradients. The dipeptide shows minimal penetration beyond the viable epidermis because its log P value below −2 restricts passive diffusion through lipid lamellae, as demonstrated by Franz diffusion cell studies using dermatomed human skin under OECD Test Guideline 428 conditions. Formulators must note that zinc pyrithione at 0.1% in anti-dandruff variants chelates the N-terminal glycine residue, reducing enzymatic release efficiency by approximately 25–35%; independent phase addition or encapsulated delivery is required when combining both actives. Batch records from pilot-scale production with rotor-stator homogenization at 8000–10,000 rpm for 10 min followed by anchor stirring at 40 rpm show no dipeptide crystallization after 6 months at 40°C/75% RH when final pH is maintained at 5.5–6.0.Enzymatic synthesis routes for specialty peptide intermediates employ Glycyl-L-leucine as a donor substrate for reverse hydrolysis and transpeptidation reactions catalyzed by immobilized proteases. The dipeptide participates as an acyl acceptor or donor in thermolysin-catalyzed condensation reactions conducted in aqueous-organic biphasic systems containing 20–40% v/v dimethylformamide or acetonitrile. At 40°C and pH 7.0 with immobilized thermolysin on Amberlite XAD-7 resin, the apparent Km for Glycyl-L-leucine is reported in peer-reviewed literature as 2–10 mM, depending on the nucleophile used. Continuous packed-bed reactors with 10 mL bed volume and residence times of 30–60 min achieve 55–75% dipeptide conversion when a second amino acid amide is supplied at 5-fold molar excess. A critical process parameter is the water activity in the organic phase; conversion drops below 20% when water content exceeds 5% v/v because hydrolytic side reactions compete with peptide bond synthesis. Operations with free thermolysin in batch mode are constrained by enzyme precipitation at acetonitrile fractions above 50% v/v, as documented in enzyme stability studies under ISO 22118:2011 reference conditions for enzymatic assay validation. Product purification requires hydrophobic interaction chromatography or cation-exchange separation because residual Glycyl-L-leucine co-elutes with many tripeptide products on reversed-phase C18 columns under standard acetonitrile gradients.Stability-Indicating Methodology Under High-Humidity Storage Conditions
Analytical characterization of Glycyl-L-leucine in raw material release and finished formulation testing relies on forced degradation profiles that establish method specificity under International Council for Harmonisation Q1A(R2) and Q2(R1) frameworks. The dipeptide reference standard stored at 25°C/60% RH in double polyethylene bags inside fiber drums shows no measurable degradation over 24 months; however, storage at 40°C/75% RH in open containers produces 0.2–0.4% free leucine after 6 months, necessitating desiccated storage for reference materials used in quantitative HPLC calibration. The assay method employs a 150 mm × 4.6 mm C18 column with 3 µm particles and a mobile phase of 10 mM sodium phosphate at pH 2.5 containing 5 mM sodium octanesulfonate to retain the polar dipeptide. Detection at 210 nm provides a limit of quantitation of 0.05% w/w for free leucine and glycine impurities relative to the dipeptide peak. Method precision studies across three independent laboratory sites show relative standard deviation below 1.5% for dipeptide content in the 95–105% label claim range.Compendial monographs under USP and Ph. Eur. specify specific optical rotation limits and related substance thresholds that batch release documentation must address. A typical acceptance criterion sets specific rotation at −24° to −30° (c = 1, water, 20°C) and individual impurity limits of 0.1% for free leucine, 0.1% for cyclo(-Leu-Gly), and 0.5% total related substances. Manufacturers of solid oral dosage forms using Glycyl-L-leucine as a taste-masking adjuvant or leucine source in medical nutrition products mill the crystalline powder through 0.5 mm screens to achieve D90 particle sizes below 150 µm for blend uniformity. Direct compression studies with dicalcium phosphate and microcrystalline cellulose show acceptable tablet hardness at 70–110 N when dipeptide content does not exceed 20% w/w; higher levels cause capping due to the brittle fracture behavior of the needle-like crystalline habit. A documented processing limitation is the dipeptide’s hygroscopicity above 60% RH, requiring granulation suites with dehumidified air supply maintained at 25–30% RH during wet granulation and drying steps.Конкурентные цены на глицил-л-лейцин, которые соответствуют вашему бюджету - гибкие условия и индивидуальные котировки для каждого заказа.
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Glycyl-L-leucine (Gly-Leu; N-glycyl-L-leucine; CAS 869-19-2) is a chiral dipeptide formed from glycine and L-leucine through a standard peptide bond. The molecular formula is C8H16N2O3, the average molecular weight is 188.23 g/mol, and the monoisotopic mass is 188.116 Da. The IUPAC name is (S)-2-(2-aminoacetamido)-4-methylpentanoic acid. In bulk and research supply chains, the product appears as a white to off-white crystalline powder; catalog model numbers are manufacturer-specific and typically encode purity tier, packaging size, and certification package rather than a single universal designation. The compound is used as a defined dipeptide substrate in aminopeptidase assays, as a hydrolysis-prone model in oligopeptide-transport experiments, and as an experimental leucine-donating component in cell culture media. No harmonized USP, EP, or JP monograph exists for glycyl-L-leucine, so product quality is specified through supplier certificates of analysis and should be evaluated against the intended assay or formulation protocol.
What Distinguishes Glycyl-L-Leucine from Related Dipeptides?
Glycyl-L-leucine contains one chiral center at the L-leucine α-carbon; this feature is absent in glycylglycine and inverted in glycyl-D-leucine. The isobutyl side chain of the leucine residue increases reversed-phase chromatographic retention and reduces aqueous solubility relative to glycine-based dipeptides. Unlike free L-leucine, the compound is transported and hydrolyzed through dipeptide-specific pathways before releasing the amino acid. Glycylglycine is achiral and used mainly as a buffer component, while glycyl-L-leucine is selected when stereochemically defined peptide cleavage or transport is under study. The table summarizes structural and functional contrasts for compounds commonly encountered in similar biochemical workflows.
| Compound | CAS registry | Molecular formula | Molecular weight | Chiral centers | Typical biochemical role |
|---|---|---|---|---|---|
| Glycyl-L-leucine | 869-19-2 | C8H16N2O3 | 188.23 g/mol | 1 L | Hydrolysis-prone dipeptide substrate |
| Glycylglycine | 556-50-3 | C4H8N2O3 | 132.12 g/mol | 0 | Achiral buffer and control dipeptide |
| L-Leucine | 61-90-5 | C6H13NO2 | 131.17 g/mol | 1 L | Free amino acid; amino acid transporter substrate |
| Glycine | 56-40-6 | C2H5NO2 | 75.07 g/mol | 0 | Free amino acid; media buffer component |
As a substrate for leucine aminopeptidase (EC 3.4.11.1), glycyl-L-leucine is hydrolyzed to glycine and L-leucine. Quantitative release of L-leucine can be monitored with ninhydrin detection at 570 nm or coupled to L-leucine dehydrogenase with NADH absorbance at 340 nm. The peptide bond is susceptible to hydrolysis, so assay buffers above pH 7.5, incubation times above 30 min at 37 °C, or residual divalent metal ions can increase background cleavage and reduce the signal window. For oligopeptide-transporter studies, glycyl-L-leucine serves as a hydrolysis-prone substrate for PEPT1/SLC15A1 and related isoforms, whereas glycylsarcosine is used when intracellular hydrolysis must be suppressed. Published apparent affinity constants for glycyl-L-leucine transport vary with expression system; apparent Km values are frequently observed in the 0.1–2.0 mM range, but each experimental platform requires independent kinetic validation. This difference is operationally important because free L-leucine generated inside cells can feedback-regulate amino acid sensing pathways and confound transport kinetics if not accounted for.
Release Specifications and the Analytical Hierarchy
Release criteria for glycyl-L-leucine are set by non-harmonized fine-chemical methods rather than a pharmacopoeial monograph. High-purity material is commonly released at 98.0–99.0% area purity by HPLC-UV, with identity confirmed by FTIR and optical rotation. Specific rotation values in supplier documentation are not harmonized; they are commonly reported near −35° at c = 2 in water, but the lot-specific certificate must be used as the operative value. The analytical hierarchy applied to incoming quality control should distinguish among purity, impurity profile, water content, and elemental burden. A peptide-like impurity that is not resolved by a generic area-percent HPLC method may still interfere in enzyme assays or cell culture growth studies. Therefore, the certificate of analysis should be read in conjunction with the specific downstream detection limit and the impurity tolerance of the biological model. System suitability criteria for chromatographic release commonly include resolution between glycyl-L-leucine and L-leucine of not less than 2.0, tailing factor not more than 1.5, and plate count not less than 2000 on a 5 µm C18 column.
| Attribute | Method basis | Typical supplier criterion |
|---|---|---|
| Identity | FTIR; optical rotation | Matches reference spectrum; rotation supplier-defined |
| Assay/purity | HPLC-UV at 214 nm | 98.0–99.0% area purity |
| Water content | Karl Fischer | ≤0.5% where specified |
| Residue on ignition | Sulfated ash, USP <281> | ≤0.1% where specified |
| Elemental impurities | ICP-MS, USP <232> | Supplier-specific; no monograph |
| Residual solvents | GC-HS, USP <467> | ICH Q3C options |
The criteria shown are not harmonized; they represent common supply-chain practices and require lot-specific verification. No ACS, USP, or EP monograph assigns legal release limits to this compound. For compositional verification, vapor-phase hydrolysis with 6 M HCl at 110 °C for 24 h releases glycine and L-leucine for amino acid analysis, which provides an orthogonal check on the claimed dipeptide structure.
When Dipeptide Substitution Enters Cell Culture Media Formulation
In chemically defined media, dipeptides can replace free amino acids to reduce osmotic pressure, limit free amino acid reactivity, or improve heat stability during media preparation. When glycyl-L-leucine is evaluated as a leucine source, the effective leucine delivery depends on dipeptide transport and intracellular hydrolase activity in the target cell line. Published data for this specific configuration is limited; glycyl-L-leucine is not established as the sole leucine source in widely adopted commercial media. The molar conversion basis is 188.23 g/mol of dipeptide providing 131.17 g/mol of L-leucine after complete hydrolysis, equivalent to 1.435 g of Gly-Leu per 1 g of L-leucine. This calculation assumes stoichiometric cleavage and conversion; actual availability depends on hydrolase capacity, and residual intact dipeptide should be tracked in spent medium if accumulation is suspected. Because one mole of glycyl-L-leucine also releases one mole of glycine, glycine-restricted or glycine-sensitive media formulations require an additional adjustment to avoid unintended shift in the glycine pool.
Physicochemical behavior in aqueous solution controls stock-solution design. Glycyl-L-leucine is zwitterionic; the terminal carboxyl pKa is estimated in the range 3.1–3.4, the terminal amino pKa in the range 7.9–8.2, and the isoelectric point lies near pH 5.5–5.8. Solubility in water is moderate but sufficient for stock solutions at 20–50 mM; higher concentrations may require gentle warming below 40 °C and pH adjustment away from the isoelectric point. Phosphate-buffered saline at pH 7.4 is compatible for short-term assay use, but prolonged aqueous storage can generate free glycine and L-leucine through slow hydrolytic cleavage even at 2–8 °C.
Enzymatic Hydrolysis Kinetics in Assay Design
Measuring initial-rate hydrolysis of glycyl-L-leucine requires control of enzyme source, metal cofactor, and detection window. Leucine aminopeptidase activity is often activated by Zn2+ or Mn2+; buffers containing EDTA or other strong chelators should be avoided because they suppress activity and obscure substrate conversion. When HPLC is used instead of a coupled enzymatic readout, gradient elution on a C18 column with UV detection at 214 nm separates glycyl-L-leucine from L-leucine, while glycine requires pre-column derivatization or an orthogonal detector because free glycine lacks a strong UV chromophore. A common chromatographic starting point is a 250 mm × 4.6 mm, 5 µm C18 column operated at 25 °C with a 0.1% trifluoroacetic acid/acetonitrile gradient. A linear calibration range is typically verified over 0.05–5.0 mM for HPLC-UV methods; values outside this range require dilution or concentration. High substrate concentrations may inhibit some aminopeptidase isoforms, and low concentrations below the validated limit yield unreliable initial slopes because detector noise limits integration at peptide wavelengths.
Thermal stress during storage and drying influences peptide integrity. Glycyl-L-leucine is typically stored desiccated at 2–8 °C for working quantities and at −20 °C or lower for reference standards; repeated freeze-thaw cycles should be avoided because moisture uptake can accelerate hydrolysis and produce batch-to-batch drift in enzyme assays. Thermal analysis generally shows decomposition rather than a sharp melting point; exact onset varies with lot purity and heating rate. Incompatibilities include strong oxidizing agents and strongly alkaline solutions. Autoclaving aqueous solutions is generally unsuitable unless stability has been demonstrated for the specific vessel, pH, and hold time. For aseptic filtration, a 0.22 µm membrane is appropriate after confirming that adsorption losses are acceptable for the target concentration.
Quality Systems and Non-Compendial Supplier Controls
For applications requiring cGMP or clinical-grade material, the absence of a glycyl-L-leucine monograph places burden on the end user to qualify the supplier and validate release methods. Compendial test chapters such as USP <232>, USP <467>, and USP <281> are commonly applied to support raw-material release even though the compound itself is non-compendial. Residual solvent limits are typically assessed under ICH Q3C options, and elemental impurity limits should follow ICH Q3D risk-based routes. Supplier audit documentation should include method validation summaries, tissue-of-origin declarations, and evidence of batch-to-batch consistency for optical rotation and chromatographic purity.
Packaging commonly spans 1 g to 1 kg for research grades; process-scale lots are typically packed in double polyethylene liners inside fiber drums with desiccant. Bulk material should be opened under low-humidity conditions when tight moisture limits are specified, and dry powder handling should be conducted with local exhaust ventilation if dust generation is anticipated.
