tBOOH acts as a suicide substrate for catalase

Area of Science:

• Biochemistry
• Enzymology
• Oxidative Stress

Background:

• Catalase is a crucial enzyme protecting cells from oxidative damage.
• T-butyl hydroperoxide (tBOOH) is a known substrate for catalase.
• Understanding enzyme-substrate interactions is vital for cellular protection mechanisms.

Purpose of the Study:

• To investigate the effects of t-butyl hydroperoxide (tBOOH) on bovine liver catalase.
• To elucidate the mechanism of catalase destruction by tBOOH in the absence of hydrogen donors.
• To examine the protective role of hydrogen donors against tBOOH-induced enzyme degradation.

Main Methods:

• UV/Vis spectroscopy to monitor spectral changes (Soret band).
• Measurement of iron release from the enzyme.
• Assay of catalatic activity via oxygen release from hydrogen peroxide.
• Electrophoretic analysis to detect structural alterations.

Main Results:

• tBOOH causes bovine liver catalase destruction via compound II formation.
• Enzyme destruction is evidenced by decreased Soret band, iron release, and reduced catalatic activity.
• Hydrogen donors (NADH, o-dianisidine) protect catalase from destruction but induce electrophoretic mobility changes.
• tBOOH is reduced to t-butanol in the presence of hydrogen donors.

Conclusions:

• Catalase acts as an internal hydrogen donor, leading to its own destruction when reacting with tBOOH without external donors.
• Hydrogen donors mitigate tBOOH-induced catalase inactivation but alter enzyme structure.
• The protective mechanism involves a peroxidase-like reaction where tBOOH is reduced to t-butanol.