Triplet Acetone Generation by Pseudoperoxidase Activity of Myoglobin: Structural Damage and Quenching.

Triplet-state carbonyl species can be generated in vivo through the oxidation of suitable substrates catalyzed by heme proteins and peroxynitrite, suggesting their involvement in metabolic processes and oxidative stress. In this work, we identified the formation of electronically excited triplet-state acetone during the aerobic oxidation of isobutanal (IBAL) initiated by ferrimyoglobin (ferriMb). This system was compared with the well-established IBAL/horseradish peroxidase (HRP) chemiluminescent reaction. Evidence for triplet acetone formation included Soret band spectral changes during the reaction, ultraweak light emission, and sodium 9,10-dibromoanthracene-2-sulfonate (DBAS)-promoted enhanced emission, as well as quenching by diene quenchers like sorbic acid and ethyl sorbate. Oxygen uptake measurements obeyed first-order kinetics in oxygen concentration for the ferriMb system. Induced structural modification of ferriMb by IBAL was identified. Together, these findings suggest that ferriMb may drive the generation of harmful triplet species under carbonyl stress. Notably, rhabdomyolysis is reportedly known as an injurious condition in which free myoglobin is present in the bloodstream.