Peptides are short chains of amino acids linked by peptide bonds. Typically, peptides contain less than 50 amino acids. Anything longer is generally referred to as a protein. However, there is no definitive molecular weight cut-off distinguishing peptides from proteins.
Key features of peptides:
- Composed of amino acids linked by peptide bonds
- Usually contain less than 50 amino acids
- Can be linear or cyclic
- Often derived from partial hydrolysis of proteins
- More stable and soluble than proteins
Peptides play numerous crucial roles in the human body:
- Act as hormones like insulin, oxytocin, and glucagon to regulate physiological processes
- Transmit signals between cells as neurotransmitters and neuromodulators
- Fight infection as part of the immune system
- Transport minerals and nutrients like iron and copper
What gives peptides their diverse functionality? Their amino acid sequence and structure. By stringing different amino acids together in various conformations, peptides gain specific shapes and properties tailored to their biological role.
For example, the peptide hormones insulin and glucagon have distinct sequences enabling them to facilitate energy storage versus energy mobilization, respectively. Antimicrobial peptides contain high proportions of hydrophobic amino acids to help them disrupt bacterial cell membranes.
Peptides also offer advantages over proteins for drug development:
- Higher activity per unit mass
- Better penetration into cells
- Less likely to induce immune responses
Hence, there is growing interest in peptide-based drugs and research into discovering new bioactive peptides encoded within proteins. Common sources of peptide pharmaceuticals include:
- Partial digestion of proteins
- Chemical synthesis
- Recombinant DNA technology
In summary,
peptides are versatile, multifunctional chains of amino acids with great therapeutic promise. Their sequence specificity allows fine-tuned targeting of biological processes—a key asset. Peptides will likely continue enjoying increased applications due to these standout traits.