Zymogen
Zymogen , noun
[Zyme + -gen.]
(Physiology Chemistry) A mother substance, or antecedent, of an enzyme or chemical ferment; -- applied to such substances as, not being themselves actual ferments, may by internal changes give rise to a ferment.
The pancreas contains but little ready-made ferment, though there is present in it a body, zymogen, which gives birth to the ferment.