# Insulin (human) > The archetypal protein biologic — a 51-amino-acid two-chain hormone, disulfide-linked, and the first recombinant DNA drug ever marketed. - Also known as: Recombinant human insulin, rhInsulin, regular insulin, Humulin, Novolin - Class: Metabolic - FDA approved: Yes - Canonical page: https://www.americanpeptide.com/catalog/insulin ## Overview Insulin is the hormone that defined the biologic era. It is a small but genuinely complex protein: two peptide chains — an A chain of 21 residues and a B chain of 30 — held together by two interchain disulfide bonds, with a third disulfide looping within the A chain. At ~5.8 kDa it is the smallest hormone in this catalog’s biologic tier, yet it is assembled, folded, and processed exactly like the larger proteins, and it was the molecule that proved recombinant human therapeutics were possible. Insulin is synthesized in the body as a single chain — preproinsulin → proinsulin — that folds and forms its disulfide bonds before a connecting C-peptide is excised, leaving the mature two-chain hormone. That biosynthetic detail is why early recombinant manufacturing expressed the A and B chains (or proinsulin) in bacteria and then handled folding and disulfide pairing as a controlled step: the chemistry that the body does enzymatically has to be reproduced and verified in a reactor. Get the disulfides wrong and you get a misfolded, inactive — or immunogenic — product. Its history is foundational twice over. Insulin was discovered in 1921 in Toronto by Banting, Best, Macleod, and Collip, and the patent was famously sold to the university for one dollar on the principle that "insulin belongs to the world." Six decades later, in 1982, recombinant human insulin (Humulin) became the first recombinant-DNA drug ever approved — the proof of concept for the entire modern biologic industry, including most of the engineered peptides elsewhere in this catalog. And then the American drama. Despite the dollar patent and a century of manufacturing experience, US insulin list prices roughly tripled between 2002 and 2013, pushing some patients to ration a drug they cannot live without — a recurring, deadly access failure that sits uncomfortably against the molecule’s origin story. For a reference that takes provenance and honest pricing seriously, insulin is the clearest case study in the gap between what a medicine costs to make and what it is sold for. Insulin is also widely misunderstood at the edges: it is occasionally misused in bodybuilding for its anabolic effects, where dosing errors cause life-threatening hypoglycemia, and the modern GLP-1 era has shifted public perception of what "diabetes medicine" even means. It remains, first and foremost, essential replacement therapy for type 1 diabetes and an important tool in advanced type 2. ## Mechanism Binds the insulin receptor, a tyrosine kinase, triggering autophosphorylation and the PI3K/AKT cascade that drives GLUT4 translocation and glucose uptake into muscle and fat, suppresses hepatic glucose output, and promotes glycogen, lipid, and protein synthesis. ## Chemistry | Property | Value | | --- | --- | | Molecular formula | C257H383N65O77S6 | | Molecular weight | 5808 Da | | CAS number | 11061-68-0 | ## Sequence ``` A chain: GIVEQCCTSICSLYQLENYCN | B chain: FVNQHLCGSHLVEALYLVCGERGFFYTPKT ``` ## Research areas Studied in: Type 1 diabetes, Type 2 diabetes, Glucose metabolism, Anabolic signaling. Guides on this site: - [Weight Loss & Metabolic Health](https://www.americanpeptide.com/research-areas/weight-loss): Incretin and metabolic peptides studied for glycemic control and fat loss. ## Key research - Type 1 diabetes — life-sustaining replacement therapy; the body produces no insulin without it. - Type 2 diabetes — used when oral agents and incretins no longer maintain glycemic control. - Insulin-receptor signaling — the PI3K/AKT and MAPK pathways that make it a central anabolic and metabolic hormone. - Analog engineering — rapid-acting (lispro, aspart) and long-acting (glargine, detemir) analogs re-engineer the sequence/formulation to reshape the absorption curve. - First recombinant drug — Humulin (1982) established recombinant human protein manufacturing. - Hypoglycemia risk — narrow therapeutic margin; misuse outside medical supervision is dangerous. ## Storage, handling & synthesis **Storage.** Unopened insulin is refrigerated (2–8 °C); in-use vials/pens are typically kept at room temperature for a limited number of days per the product label. It must not be frozen — freezing denatures the protein and destroys activity — and should be protected from heat and direct light. **Handling.** As a folded protein it is sensitive to heat, freezing, and agitation, which can cause aggregation (visible as clumping or frosting) and loss of potency. Aggregated insulin should never be used. **Synthesis.** Recombinant human insulin is expressed in E. coli or yeast — historically as separate A and B chains or as proinsulin — then folded, disulfide-paired, and (for the proinsulin route) enzymatically processed to remove C-peptide. Release testing is protein-specific: identity by peptide mapping and mass spectrometry, correct disulfide connectivity, potency by bioassay, plus host-cell-protein and endotoxin limits. This is biologic manufacturing, not peptide synthesis. ## FAQs ### What is human insulin? A 51-amino-acid protein hormone made of two disulfide-linked chains that lowers blood glucose by driving its uptake into cells. Recombinant human insulin is produced in engineered bacteria or yeast and was the first recombinant-DNA drug approved (1982). ### Why is insulin considered a biologic and not just a peptide? It is a folded, multi-chain protein whose activity depends on correct disulfide pairing, and it is produced in living cells. Its manufacturing and quality control are protein-grade, not the solid-phase synthesis used for short research peptides. ### Why is insulin so expensive in the US if the patent was sold for a dollar? The original patent was sold for $1, but modern insulin products, manufacturing, and the US pricing system are separate from that history. List prices rose sharply in the 2000s–2010s, a widely documented access problem. ### Is this medical advice? No. This is a research and educational reference. Insulin has a narrow safety margin and is a prescription medicine; nothing here is dosing guidance. ## Latest research Recent trials and publications mentioning Insulin, pulled automatically from ClinicalTrials.gov and PubMed (unfiltered search results, refreshed daily). ### Recent trials - [A Study to Evaluate MAR002 for Acromegaly](https://clinicaltrials.gov/study/NCT07641179) — NOT_YET_RECRUITING · PHASE2 · NCT07641179 - [Long-term Adaptations of Skeletal Muscle After Hybrid Training](https://clinicaltrials.gov/study/NCT07341711) — RECRUITING · NA · NCT07341711 - [Low Dose Aspirin for the Prevention of Postpartum Related Breast Cancer](https://clinicaltrials.gov/study/NCT05557877) — RECRUITING · PHASE2 · NCT05557877 - [Effects of Meal Macronutrients on Postprandial Lipids](https://clinicaltrials.gov/study/NCT07313787) — NOT_YET_RECRUITING · PHASE2 · NCT07313787 - [Effect of FMD on Colorectal Cancer Patients](https://clinicaltrials.gov/study/NCT05384444) — ACTIVE_NOT_RECRUITING · NA · NCT05384444 - [Tirzepatide's Role in Postmenopausal HR+ Breast Cancer Survivors](https://clinicaltrials.gov/study/NCT07257484) — RECRUITING · PHASE4 · NCT07257484 --- Source: AmericanPeptide.com — https://www.americanpeptide.com/catalog/insulin Data license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Attribution: AmericanPeptide.com. Research reference only — computational and educational content, not medical advice.