peptides

Definition

Short chains of amino acids linked by peptide bonds, typically containing fewer than 20–50 residues; function as signaling molecules, antimicrobial agents, toxins, and metabolic regulators in arthropod biology. In insects and arachnids, peptides serve critical roles as neuropeptides that regulate molting, reproduction, and feeding behavior; as antimicrobial peptides (AMPs) that provide innate immunity against pathogens; and as venom components in spiders, scorpions, and some wasps and ants, where they disrupt ion channels or neurotransmission in prey or predators.

Etymology

From Greek peptos, 'digested', reflecting their origin from protein breakdown.

Example

Mastoparan, a peptide in wasp venom, triggers mast cell degranulation and membrane disruption; defensins and cecropins are antimicrobial peptides produced by fat body cells in insects in response to bacterial infection.

Synonyms

• oligopeptides

Related Terms

• neuropeptides
• amino acids
• proteins
• venom
• antimicrobial peptides
• pheromones
• peptide bond
• Proteomics

Usage Notes

Distinction from proteins is operational rather than absolute: peptides are shorter (generally <10 kDa or <50 residues), often lack stable tertiary structure, and are frequently synthesized non-ribosomally or through specialized post-translational processing. In arthropod research, 'peptide' often implies bioactive function (hormone, toxin, or immune effector) rather than mere size. Contrast with 'polypeptide' (longer chain, often protein precursor) and 'peptidomimetic' (synthetic compound mimicking peptide activity). Many arthropod peptides are amidated at the C-terminus, a modification critical for receptor binding and metabolic stability.