Protease

Definition

An enzyme that catalyzes proteolysis by hydrolyzing peptide bonds within proteins, cleaving them into smaller polypeptides or free amino acids. In arthropods, proteases serve critical digestive functions—particularly in the midgut lumen where they break down dietary proteins—and participate in developmental remodeling, immune activation (e.g., prophenoloxidase cascade), and venom composition. Major classes include serine proteases (trypsin, chymotrypsin), cysteine proteases, aspartic proteases, and metalloproteases, distinguished by their catalytic mechanism and active-site residues.

Etymology

From protein + -ase (enzyme suffix)

Example

Mosquito larvae secrete trypsin-like serine proteases into the midgut to degrade blood meal proteins; some spider venoms contain metalloproteases that disrupt vertebrate tissue integrity by cleaving extracellular matrix components.

Synonyms

• peptidase
• proteinase

Related Terms

• proteolysis
• Enzyme
• digestion
• Midgut
• venom
• serine protease
• trypsin
• chymotrypsin
• metalloprotease
• prophenoloxidase cascade
• peptide bond

Usage Notes

Specialists distinguish 'protease' (broad, any enzyme cleaving peptide bonds) from 'proteinase' (often reserved for endopeptidases acting on intact proteins) and 'peptidase' (IUBMB nomenclature encompassing both exopeptidases and endopeptidases). In entomology, context usually clarifies whether digestive, immune, or venom proteases are intended. Serine proteases dominate arthropod digestion, whereas metalloproteases and cysteine proteases are more common in venoms and some parasitoid secretions.