Proenzymes

Part of speech: noun

Definitions

1. Inactive precursors of enzymes, which require activation for their enzymatic function
2. Biologically inactive forms of enzymes that must undergo a transformation to become functional
3. Substrates that operate as enzyme precursors, necessitating activation to catalyze biochemical reactions

Etymology: Proenzymes is the plural of "proenzyme", a term built from the prefix "pro-" and "enzyme". The prefix comes from Greek "pro", meaning "before" or "in front of", and it signals that the substance comes before, or is a precursor to, the active form. A proenzyme is an enzyme that is produced in an inactive state and must be altered before it can work. The plural of the noun is simply formed by adding "-s", so the word refers to several such inactive enzyme forms at once. Its meaning rests entirely on the sense of "pro-" as "before", which gives the whole word its logic: the enzyme exists in a prepared stage ahead of its functional stage.

Synonyms: zymogens, precursor enzymes