The Collaborative International Dictionary of English v.0.48:

inactivate \inactivate\ v. t. [imp. & p. p. inactivated; p.
   pr. & vb. n. inactivating.]
   to make inactive; as, boiling will inactivate most enzymes;
   acetylation of the antibiotic inactivated it.

   Syn: deactivate.
        [WordNet 1.5 +PJC]

   Note: To inactivate an enzyme or chemical usually renders it
         permanently inactive; to inactivate a machine (as by
         turning a switch) may be reversible, and for machines
         and devices, the term deactivate is usually used. The
         distinction is worth preserving.
         [PJC]