Types of Peptides and Their Uses: From Signalling to Skincare

Peptides are remarkably diverse molecules with functions spanning nearly every aspect of biology. Understanding the different types of peptides and their specific uses is essential for UK researchers, clinicians, and anyone interested in the science behind these powerful biomolecules.

This guide categorizes peptides by their functional roles and explores their applications in research, medicine, and biotechnology.

Classification by Functional Role

1. Signal Peptides

Signal peptides (also called signaling or messenger peptides) are molecules that transmit information between cells, tissues, and organs. They're among the most studied and therapeutically relevant peptide types.

Hormonal Peptides

These regulate metabolic and physiological processes:

• Insulin (51 aa): Regulates glucose uptake and metabolism. The first peptide drug (discovered 1921, synthesized 1963).
• Glucagon (29 aa): Raises blood glucose by promoting glycogen breakdown.
• Growth Hormone (191 aa): Though technically a small protein, it regulates growth and metabolism.
• GLP-1 (Glucagon-Like Peptide-1): Regulates insulin secretion and appetite. The basis for drugs like semaglutide and liraglutide.

Growth Hormone Secretagogues (GHS)

These stimulate the release of growth hormone:

• GHRP-6 and GHRP-2: Early synthetic GH-releasing peptides
• Ipamorelin: Selective GH secretagogue with fewer side effects
• CJC-1295: Long-acting GHRH analog
• Hexarelin: Potent GH secretagogue also studied for cardiac effects

Neuropeptides

Function in neural communication and brain function:

• Oxytocin (9 aa): Social bonding, trust, childbirth, lactation
• Vasopressin/ADH (9 aa): Water retention, blood pressure regulation
• Substance P (11 aa): Pain perception, inflammation
• Neuropeptide Y (36 aa): Appetite regulation, stress response
• Semax and Selank: Russian nootropic research peptides

2. Carrier Peptides

These peptides bind and transport important trace elements or molecules to cells:

• GHK-Cu (Copper Peptide): Carries copper ions, studied for wound healing and skin regeneration. Popular in anti-aging skincare.
• Transferrin peptides: Iron transport
• Metallothionein fragments: Bind heavy metals

Research Applications: Cosmeceuticals, wound healing studies, targeted nutrient delivery

3. Enzyme Inhibitor Peptides

These block the activity of specific enzymes:

ACE Inhibitors

Inhibit Angiotensin-Converting Enzyme, lowering blood pressure:

• Captopril: The first ACE inhibitor drug (though technically not a peptide in its final form, it was developed from snake venom peptides)
• Food-derived peptides: Milk casein and soy peptides with ACE-inhibitory activity

Protease Inhibitors

• Aprotinin: Serine protease inhibitor used in surgery to reduce bleeding
• Bowman-Birk inhibitors: Found in legumes, studied for cancer prevention

4. Antimicrobial Peptides (AMPs)

Part of the innate immune system, these kill or inhibit bacteria, fungi, and viruses:

Defensins

Small (15-50 aa) cationic peptides with broad-spectrum antimicrobial activity:

• α-Defensins: Found in neutrophils and intestinal Paneth cells
• β-Defensins: Produced by epithelial cells

Cathelicidins

• LL-37: The only human cathelicidin, with antimicrobial and immunomodulatory properties

Synthetic AMPs

• Pexiganan: Synthetic AMP based on magainin (from frog skin)
• Nisin: Bacteriocin used as food preservative

Research Focus: Alternative to traditional antibiotics for resistant infections, wound healing, preservatives

5. Healing and Regenerative Peptides

These promote tissue repair and regeneration:

Thymosin Family

• TB-500 (Thymosin Beta-4): Promotes cell migration, angiogenesis, wound healing
• Thymosin Alpha-1: Immune system modulation, studied for infections and cancer

Body Protection Compound

• BPC-157: Derived from gastric juice protein, studied for healing effects in animal models

Growth Factors (small peptides)

• IGF-1 LR3: Modified insulin-like growth factor
• PEG-MGF: Mechano Growth Factor variant

6. Metabolic and Longevity Peptides

These influence metabolism, mitochondrial function, and aging:

• 5-Amino-1-MQ: NNMT inhibitor studied for fat metabolism
• AOD-9604: Fragment of growth hormone studied for fat metabolism
• MOTS-c (16 aa): Mitochondrial peptide studied for metabolic regulation and exercise response
• SS-31 (Elamipretide): Mitochondrial-targeting peptide for mitochondrial diseases
• Epitalon (4 aa): Russian peptide studied for telomerase activation and longevity
• NAD+ precursors: Though not peptides themselves, often discussed alongside peptides in longevity research

7. Cosmetic and Dermatological Peptides

Popular in skincare for anti-aging and skin repair:

Signal Peptides for Collagen

• Palmitoyl Pentapeptide (Matrixyl): Claimed to stimulate collagen synthesis
• Palmitoyl Tripeptide-1: TGF-β stimulation

Neurotransmitter-Affecting Peptides

• Acetyl Hexapeptide-8 (Argireline): "Botox-like" effect by reducing muscle contractions
• Pentapeptide-18 (Leuphasyl): Similar mechanism to Argireline

Carrier Peptides

• GHK-Cu: Copper delivery for wound healing and collagen synthesis

8. Cell-Penetrating Peptides (CPPs)

These can cross cell membranes, useful for drug delivery:

• TAT peptide: From HIV-1 Tat protein, enables cellular uptake
• Penetratin: From Antennapedia homeodomain
• Transportan: Chimeric peptide combining galanin and mastoparan

Applications: Delivering drugs, nucleic acids, or proteins into cells for research and therapy

9. Immunomodulatory Peptides

Modulate immune system function:

• Thymosin Alpha-1: Enhances T-cell function, studied for infections and cancer
• LL-37: Beyond antimicrobial effects, modulates inflammation and wound healing
• Vasoactive Intestinal Peptide (VIP): Anti-inflammatory, studied for autoimmune conditions

10. Melanocortins and Tanning Peptides

Activate melanocortin receptors involved in pigmentation and other functions:

• Melanotan II: Synthetic analog of α-MSH, stimulates melanogenesis (tanning) and has other effects
• Melanotan I (Afamelanotide): Licensed in some countries for erythropoietic protoporphyria
• PT-141 (Bremelanotide): Derived from Melanotan II, studied for sexual dysfunction

Classification by Chemical Structure

Linear Peptides

Straight chain without cyclization. Most synthetic peptides are linear.

Examples: BPC-157, TB-500, most GHRPs

Cyclic Peptides

Form a closed loop, often more stable and resistant to degradation.

Examples: Oxytocin, vasopressin, cyclosporine (immunosuppressant)

Modified Peptides

• PEGylated: Attached to polyethylene glycol for extended half-life
• Acetylated/Amidated: End-capping for stability
• D-Amino Acid Substitution: Increased resistance to enzymatic degradation
• Stapled Peptides: Intramolecular cross-links for enhanced stability and cell penetration

Classification by Origin

Endogenous Peptides

Naturally produced in the human body:

Examples: Insulin, glucagon, oxytocin, endorphins

Exogenous Peptides

From external sources or synthetic:

• Food-derived: Casein peptides, soy peptides, collagen peptides
• Venom-derived: ACE inhibitors from snake venom, ziconotide (pain medication from cone snail)
• Fully synthetic: BPC-157, many GHRPs, cosmetic peptides

Therapeutic Applications by Category

Diabetes and Metabolic Disorders

• Insulin, GLP-1 agonists (semaglutide, liraglutide, tirzepatide), glucagon

Cancer

• Immunomodulatory peptides, targeted peptide-drug conjugates, vaccine peptides

Cardiovascular

• ACE inhibitor peptides, natriuretic peptides (BNP for heart failure)

Infectious Diseases

• Antimicrobial peptides, antiviral peptides, antifungal peptides

Pain Management

• Ziconotide (Prialt), endorphin analogs

Osteoporosis

• Teriparatide (PTH fragment), abaloparatide

Research Applications

• Drug Discovery: Peptides as lead compounds for developing small molecule drugs
• Diagnostics: Peptide biomarkers, imaging agents
• Cell Biology: Growth factors for cell culture, differentiation studies
• Immunology: Vaccine development, epitope mapping
• Structural Biology: Model systems for protein folding and function

UK Regulatory Context

For researchers in the UK, understanding regulatory status is important:

• Licensed Medicines: Insulin, GLP-1 agonists, etc. - require prescription
• Research Chemicals: BPC-157, TB-500, most GHRPs - legal for research only, not human consumption
• Banned Substances: Many peptides are on WADA's prohibited list for competitive sports
• Cosmetic Ingredients: Must comply with UK/EU cosmetics regulations

Conclusion

The world of peptides is vast and diverse, spanning from naturally occurring hormones to synthetic research compounds, from life-saving diabetes medications to anti-aging skincare ingredients. Understanding the different types of peptides and their specific functions is crucial for:

• UK researchers selecting appropriate peptides for studies
• Clinicians considering peptide therapeutics
• Anyone interested in the science behind these remarkable molecules

As peptide science continues to advance, new categories and applications will emerge, further expanding the already impressive versatility of these biomolecules. Whether in medicine, research, cosmetics, or biotechnology, peptides will continue to play an increasingly important role in improving human health and advancing scientific knowledge.

Disclaimer: This article is for educational purposes. Research peptides are for laboratory use only and not approved for human consumption.