activator

noun
  1. 1

    One who, or that which, activates.

  2. 2

    Something that activates a catalyst

  3. 3

    Any chemical or agent which regulates one or more genes by increasing the rate of transcription.

  4. 4

    A type of effector that increases the rate of enzyme-mediated reactions.

  5. 5

    A type of dopant used in phosphors and scintillators.

  6. 6

    An agent that enables the flotation of a mineral or minerals.

Source: https://en.wiktionary.org/wiki/activator