proenzyme

The precursor of an enzyme, requiring some change (usually the hydrolysis of an inhibiting fragment that masks an active grouping) to render it active; e.g., pepsinogen, trypsinogen, profibrolysin. SYN: zymogen.

* * *

pro·en·zyme (')prō-'en-.zīm n ZYMOGEN

* * *

(zymogen)

n.

the inactive form in which certain enzymes (e.g. digestive enzymes) are originally produced and secreted. The existence of this inactive form prevents the enzyme from breaking down the cells in which it was made. Once the proenzyme has been secreted it is converted to the active form.

* * *

pro·en·zyme (pro-enґzīm) an inactive precursor that can be converted to the active enzyme. Proenzymes, containing extra-long polypeptide chains that block activity, are activated by acid or enzymatic hydrolysis to remove the inhibiting portion.