Digestive enzyme secretion

Definition

The regulated release of hydrolytic enzymes into the digestive tract or onto food by specialized cells or glands, enabling the extracellular or intracellular breakdown of macromolecules. In arthropods, this process involves distinct regional specializations: salivary glands and the anterior midgut typically secrete enzymes for initial extracellular digestion, while the posterior midgut and gastric caeca often produce membrane-bound or secreted enzymes for terminal digestion and nutrient absorption. The process is controlled by neural and hormonal signals responding to feeding state, food quality, and developmental stage.

Etymology

Example

In the tobacco hornworm (Manduca sexta), digestive enzyme secretion shifts dramatically during the final larval instar: the anterior midgut secretes trypsin and chymotrypsin into the gut lumen upon feeding, while the posterior midgut upregulates membrane-anchored aminopeptidases for peptide absorption; this regional partitioning allows efficient protein digestion without autolysis of the gut epithelium.

Synonyms

• enzyme release
• gut secretory activity

Related Terms

• Midgut
• salivary gland
• peritrophic matrix
• extracellular digestion
• intracellular digestion
• gastric caeca
• digestive physiology
• Protease
• amylase
• lipase

Usage Notes

Distinguish from enzyme synthesis (transcription/translation) and enzyme activation (zymogen cleavage). In many insects, secretion and synthesis are coupled—feeding triggers both—but some species store pre-formed enzymes in secretory granules for rapid release. Contrast with 'enzyme excretion,' which implies loss from the body. The term is usually applied to the regulated apical release of enzymes into the gut lumen; basolateral release into the hemolymph is rare and typically pathological.