An enzyme that ships in a switched-off state and gets activated later by a chemical cut that removes an inhibitory piece — like an enzyme with a safety pin that needs to be pulled.Zymogens (also called proenzymes) prevent uncontrolled enzymatic activity by keeping the enzyme inactive until activation is needed. POMC processing is an example of zymogen-like precursor activation — prohormone convertases PC1 and PC2 cleave POMC at specific sites to release ACTH, α-MSH, and other bioactive peptides at the right time and place. The coagulation cascade involves multiple zymogens activated in sequence. Peptide anticoagulants like bivalirudin and eptifibatide act on already-activated clotting enzymes (thrombin and Factor Xa respectively).Note: This glossary is for educational purposes only. Definitions reflect standard usage in the research literature and do not constitute medical advice.