GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

11. FUNDAMENTAL MECHANISMS OF METABOLISM AND ENERGY CONVERSION IN MICROORGANISMS

11.6. ELECTRON TRANSPORT CHAIN AND PHOSPHORYLATION (ATP SYNTHESIS) DURING ELECTRON TRANSFER

11.6.7. Toxic effect of molecular oxygen on aerobic and anaerobic microorganisms

Oxygen serves as the terminal electron acceptor during aerobic Respiration and is therefore essential for all aerobic organisms. Since the time of L. Pasteur, it has been known that oxygen is toxic to anaerobes. Somewhat unexpectedly, it was later discovered that oxygen can also exert toxic effects on aerobes. Consequently, most organisms possess Enzymes capable of protecting The Cell from the toxic derivatives of oxygen, which include hydrogen peroxide, superoxide and hydroxyl radicals, and singlet oxygen. Key Enzymes of this protective system are catalase and peroxidase, which break down hydrogen peroxide:

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The enzyme responsible for neutralizing superoxide radicals is superoxide dismutase

As seen from the reaction above, superoxide dismutase converts superoxide radicals into hydrogen peroxide, which is subsequently decomposed by catalase or peroxidase.