Zero-point energies (ZPEs) of intermolecular, noncovalent vibrations and isotope effects, induced by noncovalent interactions, are computed for complexes of lipoxygenase, which induces enzymatic oxidation of arachidonic acids in living organisms. For complexes with hydrogen, water, methane, and ethylene molecules noncovalent isotope effects are in the range 1.2–1.8, i.e. these isotope effects are much less than the experimentally detected effects induced by tunneling.