EXPERIMENTAL-EVIDENCE FOR THE COEXISTENCE OF OSCILLATORY AND STEADY-STATES IN THE PEROXIDASE-OXIDASE REACTION

Experiments are reported that demonstrate the coexistence of periodic oscillations and a stable steady state in the aerobic oxidation of NADH catalyzed by horseradish peroxidase. This coexistence was generally observed when the enzyme concentration is low, typically around 0.5 μM. In agreement with the predictions of the computer simulations performed by Aguda and Larter (J. Am. Chem. Soc. 1990, 112, 2167-2174), it was observed that cutting off the oxygen supply temporarily will switch the steady state to the oscillatory state; the reverse process was accomplished by spiking the reaction system with hydrogen peroxide. Bursting oscillations interrupted by long near-steady-state phases were also observed and are interpreted as switching between the oscillations and steady state either due to experimental fluctuations or to the emergence of a Hopf bifurcation resulting from a change in the NADH concentration. © 1990, American Chemical Society. All rights reserved.