The Collaborative International Dictionary of English v.0.48:

catalase \catalase\ n.
   an enzyme found in most plant and animal cells that functions
   as an oxidative catalyst; it decomposes hydrogen peroxide
   into hydrogen and water.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

catalase
    n 1: enzyme found in most plant and animal cells that functions
         as an oxidative catalyst; decomposes hydrogen peroxide into
         oxygen and water