Inactivation of enzyme: Why inactivation constants do not follow the Arrhenius equation?
Without attempting to elaborate (this is not my area of expertise) I rely on the abstract to an article [1] reviewing the subject for an answer: 


  The Arrhenius equation has been widely used as a model of the
  temperature effect on the rate of chemical reactions and biological
  processes in foods. Since the model requires that the rate increase
  monotonically with temperature, its applicability to enzymatic
  reactions and microbial growth, which have optimal temperature, is
  obviously limited. This is also true for microbial inactivation and
  chemical reactions that only start at an elevated temperature, and for
  complex processes and reactions that do not follow fixed order
  kinetics, that is, where the isothermal rate constant, however
  defined, is a function of both temperature and time.


Reference

[1] Peleg et al Critical reviews in food science and nutrition 52(9):830-51 (2012)