What is a peptide?

What is a Peptide?

A peptide is a short chain of amino acids linked together by peptide bonds, typically consisting of 2 to approximately 50 amino acids, distinguishing them from proteins which contain more than 50 amino acids. 1, 2

Basic Structure and Definition

• Peptides are molecules composed of at least two amino acids connected by peptide bonds, which are chemical linkages formed between the carboxyl group of one amino acid and the amino group of another 1, 2

• The classification of peptides versus proteins is primarily based on size and structure:

  • Oligopeptides contain fewer than 10-20 amino acids 1
  • Polypeptides consist of 20-50 amino acids 1
  • Proteins typically contain more than 50 amino acids and often include multiple peptide subunits 1

• The shorter chain length of peptides is the key characteristic that distinguishes them from larger protein molecules 2

Biological Significance

• Beyond their nutritional properties, peptides serve as structural components of hormones, enzymes, toxins, and antibiotics, playing fundamental physiological roles throughout the body 1

• Peptides function in diverse biological processes including:

  • Hormone regulation 3
  • Neurotransmission 3
  • Immune modulation 3

Therapeutic Applications

• Peptides are recognized for being highly selective and efficacious while remaining relatively safe and well-tolerated, which has driven increased pharmaceutical interest 4

• Since the introduction of insulin as the first commercial peptide drug, more than 80 peptide-based drugs have reached the market for conditions including diabetes, cardiovascular diseases, urological disorders, HIV, multiple sclerosis, osteoporosis, chronic pain, and cancer 1, 3

• Approximately 140 peptide therapeutics are currently being evaluated in clinical trials, demonstrating ongoing advancement in this field 4

Examples in Clinical Medicine

• Calcitonin salmon is a synthetic polypeptide of 32 amino acids used therapeutically, demonstrating how peptides function as active pharmaceutical agents 5

• Tirzepatide is a synthetic peptide with dual-hormone agonistic activity at both GLP-1 and GIP receptors, exemplifying modern peptide drug design 6

• The efficacy of therapeutic peptides depends on precise molecular modifications that prevent rapid degradation and provide appropriate pharmacokinetic properties 6