The Peroxidase-NADH Biochemical Oscillator. 2. Examination of the Roles of Hydrogen Peroxide and Superoxide

Article abstract of DOI:10.1021/j100004a022

The peroxidase-NADH oscillator examined here initially consists of a well-mixed aqueous solution of native horseradish peroxidase, reduced β-nicotinamide adenine dinucleotide (NADH), methylene blue (MB⁺), and dissolved oxygen combined in a semi-batch reactor under a set of standard conditions.Hydrogen peroxide and superoxide have been implicated as important chemical intermediates.A comprehensive model which includes such intermediates and all initial chemical species has appeared elsewhere.To experimentally explore the role of hydrogen peroxide in the oscillator, H2O2 was substituted for MB⁺ as an initial ingredient.This substitution allows relatively small, quasi-sinusoidal oscillations sensitive to the oxygen mass transport constant, and predicted earlier in a theoretical model.The oscillations become much larger when MB⁺ is added, suggesting that MB⁺ might serve as a chemical mediator between the small oscillations seen when H2O2 is substituted for MB⁺, and the relatively large oscillations observed when MB⁺ is present.Catalase and superoxide dismutase are used as enzymatic scavengers for H2O2 and O2^.-, respectively.The enzymes are added individually to a working oscillator at oxygen minima and maxima to examine the roles and approximate the concentrations of H2O2 and O2^.-.For the enzyme addition experiments, a perturbation model for oxygen behavior is proposed and applied to the interpretation of experimental data.Two methods of analysis for the addition of the enzyme probes indicate a higher concentration of H2O2 and O2^.- at oxygen maxima than at minima.Comparison of experimental and simulated data indicate that the relatively simple model presented here is a resonable, yet apparently incomplete, representation of oxygen dynamics for the addition of scavenger enzymes to this oscillator.