Peptides are biomolecules composed of short chains of amino acids linked through covalent peptide bonds (amide linkages). Typically, peptides contain between 2 and 50 amino acid residues, distinguishing them from larger proteins, although the boundary is somewhat arbitrary. They are fundamental components in biology, bridging the gap between small molecules (like metabolites) and complex proteins.

Peptides serve diverse biological functions, including:

• Acting as hormones (insulin, glucagon) to regulate physiological processes.

• Serving as neurotransmitters and neuromodulators (endorphins, substance P).

• Functioning as antimicrobial agents in innate immunity (defensins, magainins).

• Modulating enzyme activity or signaling pathways in cells.

Synthesis of peptides occurs through several mechanisms:

• Ribosomal synthesis: Genetically encoded peptides are produced by ribosomes, forming the canonical set of proteins and peptides.

• Non-ribosomal peptide synthesis (NRPS): Observed in bacteria and fungi, producing cyclic or modified peptides like antibiotics (vancomycin, bacitracin).

• Enzymatic cleavage of precursor proteins: Produces active peptides like angiotensin or bradykinin.

• Chemical synthesis: Synthetic peptides are widely used in research, therapeutic applications, and industrial production.