191 Amino Acid Sequence (Somatropin)

191 Amino Acid Sequence — Somatropin for Laboratory Research

This category covers recombinant human growth hormone (somatropin, rhGH) with the authentic, full-length 191 amino acid sequence — identical to the hormone produced by the pituitary gland. The amino acid count in the category name is not incidental: it distinguishes somatropin from the older 192 amino acid variant (somatrem) and from growth hormone fragments. All items are chemical reagents intended for laboratory research use only (Research Use Only) — they are not medicinal products or dietary supplements. Every batch carries an HPLC ≥98% certificate and identity confirmation by mass spectrometry. Browse the available variants below.

What the 191 Amino Acid Sequence Is — Authentic Somatropin

Human growth hormone (GH) produced by the somatotropic cells of the anterior pituitary is a polypeptide of 191 amino acids with a molecular weight of approximately 22,124 Da (22 kDa) and two intramolecular disulfide bridges. Somatropin is the recombinant version of this hormone — manufactured by genetic engineering in bacterial cells (Escherichia coli) or mammalian cells — with a sequence identical to the endogenous hormone.

The term “191 amino acid sequence” is a precise signal of chemical identity. The complete, authentic human GH sequence comprises exactly 191 amino acid residues. It is this form that is the subject of research into the growth hormone axis, GH receptor signaling, and metabolism.

Why the Amino Acid Count Matters — Disambiguation

In the reagent trade and in the pharmacological history of growth hormone, three distinct entities are easily confused. The amino acid count and molecular weight on the certificate of analysis (COA) are the only reliable basis for distinguishing them.

Somatrem (192 aa) was the first recombinant form of GH introduced in the 1980s — the additional methionine at the N-terminus resulted from the bacterial expression method. Modern somatropin (191 aa) is a form with the authentic sequence, without the extra residue.

HGH Fragment 176-191 is an entirely different molecule — a short fragment covering only the C-terminal segment of the hormone (residues 176–191), studied in the context of fat metabolism. It is not full-length growth hormone and does not activate the GH receptor in the classical manner. The distinction between approaches to the growth hormone axis — secretagogue vs fragment — is discussed in the analysis MK-677 vs HGH Fragment 176-191.

For a researcher evaluating a “growth hormone” reagent, the distinction is fundamental: the amino acid sequence and molecular weight on the COA determine which molecule the vial or pen actually contains. The category name “191 amino acid sequence” unambiguously indicates authentic, full-length somatropin.

Available Variants in the Catalog

Somatropin with the 191 amino acid sequence is available in the One Peptides catalog in two physical forms of the research reagent:

Both variants contain the same active substance — recombinant somatropin 191 aa. The choice of form depends on the research protocol: the pen eliminates the reconstitution step, while the vial kit provides precise concentration control. For calculating the concentration and volume of the working solution (vial variant), the peptide calculator is helpful. The analytical quality is identical for both forms (HPLC ≥98%, MS confirmation, COA per batch).

Mechanism of Action in Research

Somatropin binds to the growth hormone receptor (GHR) — a membrane receptor from the cytokine receptor family. Binding of the hormone molecule to two receptor subunits leads to dimerization and activation of the intracellular signaling cascade:

• JAK2/STAT5 pathway — the receptor-associated kinase JAK2 phosphorylates STAT5 transcription factors, modulating the expression of growth hormone response genes
• GH-IGF1 axis — activation of GHR in the liver stimulates production of insulin-like growth factor 1 (IGF-1), which mediates many peripheral effects
• Metabolic pathways — modulation of lipid metabolism, carbohydrate homeostasis, and protein turnover in research models

The GHR receptor mechanism and JAK2/STAT5 signaling are among the well-documented pathways of molecular endocrinology — a subject of research ranging from growth physiology to energy metabolism and tissue regeneration in preclinical models.

Regulatory Status and WADA

Somatropin exists within two distinct regulatory frameworks — the distinction is fundamental for this category:

The active substance may be chemically the same, but the products come from two distinct regulatory lines. The RUO reagent in this category is not a medicine and is not intended for human use.

WADA: somatropin (growth hormone) appears on the Prohibited List in category S2 (peptide hormones, growth factors, and related substances) — the prohibition applies year-round, across all disciplines subject to anti-doping control. Athletes may not use somatropin at any time.

What Unites All Variants — Quality

Regardless of form (pen or vial kit), every batch in this category undergoes an analytical control procedure:

• HPLC ≥98% — chromatographic purity confirmed by high-performance liquid chromatography
• MS confirmation — structural identity confirmed by mass spectrometry through comparison of the measured mass with the theoretical value (~22 kDa). This is the decisive analysis for distinguishing somatropin 191 aa from variants
• COA per batch — a public certificate of analysis for each batch, with sequence and mass
• Cold chain 2–8°C — cold chain from synthesis to delivery; somatropin is a temperature-sensitive protein
• Batch traceability — batch number in three places (packaging, invoice, COA)

The certificate of analysis with mass confirmation of ~22 kDa is particularly important for this category — it is the document that unambiguously distinguishes full-length somatropin 191 aa from growth hormone fragments (~1.8 kDa) or the 192 aa variant. How to read COA parameters and what to require from a reagent supplier is described in the guide how to identify high-quality research peptides; analytical batch documentation is provided on the quality testing and certificates page.

Frequently Asked Questions

What does “191 amino acid sequence” mean?

It is the authentic, full-length sequence of human growth hormone — identical to the hormone produced by the pituitary gland. Somatropin (recombinant GH) has exactly 191 amino acid residues and a mass of ~22 kDa. The name distinguishes it from the older 192 amino acid variant (somatrem) and from growth hormone fragments.

How does somatropin 191 aa differ from somatrem 192 aa?

Somatropin has the authentic 191 amino acid sequence, identical to human GH. Somatrem is an older recombinant variant with an additional N-terminal methionine (192 amino acids, Met-GH) — derived from the early bacterial expression method of the 1980s. The mass difference of ~120 Da is visible in mass spectrometry. Modern somatropin is a form with the authentic, full-length sequence.

How does somatropin differ from HGH Fragment 176-191?

These are two distinct molecules. Somatropin (191 aa, ~22 kDa) is full-length growth hormone that activates the GH receptor. HGH Fragment 176-191 (16 amino acids, ~1.8 kDa) is a short C-terminal fragment of the hormone studied in a different context (lipid metabolism) — it is not full-length GH and does not activate the receptor in the classical manner. The molecular weight on the COA unambiguously distinguishes the two items.

How does the pen differ from the vial kit?

The pen contains pre-reconstituted somatropin, ready for sampling without a reconstitution step. The vial kit contains a lyophilizate (dry powder) requiring reconstitution in bacteriostatic water — providing full control over working solution concentration. The active substance and analytical quality are identical; they differ in physical form and convenience of laboratory work.

Is somatropin on the WADA list?

Yes. Somatropin (growth hormone) appears on the WADA Prohibited List in category S2 (peptide hormones and growth factors). The prohibition applies year-round. Athletes subject to anti-doping control may not use it at any time.

How do you read a COA for somatropin?

Two fields are decisive: the amino acid sequence (authentic somatropin = 191 residues) and the molecular weight in MS (~22,124 Da). The mass distinguishes somatropin 191 aa from somatrem 192 aa (~+120 Da) and from fragment 176-191 (~1.8 kDa). If the COA does not contain these data, ask the supplier to add them — the trade name alone does not unambiguously identify the molecule.

Product status. All items in this category are chemical reagents intended for laboratory research use only (Research Use Only) — they are not medicinal products, dietary supplements, or foodstuffs. The active substance (somatropin) is registered as a medicine only within a separate regulatory framework; the RUO reagent in this category is not a medicine and is not intended for human use. Somatropin appears on the WADA Prohibited List (category S2) — prohibited year-round. The status of each item is indicated on its product page.