Resumen de Falling Enzyme Activity as Temperature Rises: Negative Activation Energy or Denaturation?
Recently in this Journal, Aledo and coworkers used the Michaelis–Menten and Arrhenius equations to show that, under the biologically common condition of low substrate concentration, reaction rates can actually decline with increasing temperature. They presented two data sets showing a decline in lactate dehydrogenase activity above 20–30 °C as an example of this behavior. Although denaturation provides a fairly good statistical fit to the lactate dehydrogenase data sets, it is exceedingly unlikely that the activity decline above 20–30 °C is caused by denaturation. Instead, it is possible that a dramatic conformational change of the enzyme occurs in this temperature range, causing the apparent activation energy to shift from positive to negative and the frequency factor to fall by over 4 orders of magnitude. This conformational change is intriguing and worthy of further study.
