Answer: inhibitor

AnswerCrossword Clue
INHIBITORAnticatalyst
inhibitorsomething or someone that inhibits also INHIBITER
inhibitorA thing that inhibits someone or something
inhibitorA gene whose presence prevents the expression of some other gene at a different locus
inhibitorA substance that slows down or prevents a particular chemical reaction or other process, or that reduces the activity of a particular reactant, catalyst, or enzyme