Breaking down hydrogen peroxide

[Pinkleton]

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I'm a little confused on the details of how we use and get rid of hydrogen peroxide.

A figure on pg 23 on Goljan shows myeloperoxidase breaking down the peroxide to form bleach INSIDE of a phagolysome which makes sense since that's where bacteria are sequestered. It also shows the peroxide produced from respiratory burst diffusing ito the cell, where it is broken down by GSH peroxidase. Is this just excess peroxide that is made during inflammation?

What about peroxide made during metabolic processes? Are these enzymes involved in breaking that down as well? Or is that where catalase comes into play?

 

[Ycut]

As far as i know mostly catalase breaks down h2o2 and OH free radicals are neutralized by GSH peroxidase

 

[Eagle76]

I'm a little confused on the details of how we use and get rid of hydrogen peroxide.

A figure on pg 23 on Goljan shows myeloperoxidase breaking down the peroxide to form bleach INSIDE of a phagolysome which makes sense since that's where bacteria are sequestered. It also shows the peroxide produced from respiratory burst diffusing ito the cell, where it is broken down by GSH peroxidase. Is this just excess peroxide that is made during inflammation?

What about peroxide made during metabolic processes? Are these enzymes involved in breaking that down as well? Or is that where catalase comes into play?

The peroxide in the respiratory burst comes from NADPH oxidase (NOX) enzymes. There actually many different forms of NOX that may have a role in cells besides neutrophils. Anyways, NOX produces superoxide which is then rapidly dismutated into peroxide. The peroxide can then be a substrate for myeloperoxidase to produce HOCl. Excess peroxide can be degraded by both glutathione peroxidase and catalase. Generally, glutathione peroxidase can handle basal levels of peroxide from normal metabolism (GSH equivalents are needed for the reaction) while large fluxes are handled by catalase (also remember catalase is localized to the peroxisome). There are some other systems (i.e. peroxiredoxins) that also degrade peroxide, but I doubt you would ever see those on Step I.

Hope this helps.

 

[Pinkleton]

The peroxide in the respiratory burst comes from NADPH oxidase (NOX) enzymes. There actually many different forms of NOX that may have a role in cells besides neutrophils. Anyways, NOX produces superoxide which is then rapidly dismutated into peroxide. The peroxide can then be a substrate for myeloperoxidase to produce HOCl. Excess peroxide can be degraded by both glutathione peroxidase and catalase. Generally, glutathione peroxidase can handle basal levels of peroxide from normal metabolism (GSH equivalents are needed for the reaction) while large fluxes are handled by catalase (also remember catalase is localized to the peroxisome). There are some other systems (i.e. peroxiredoxins) that also degrade peroxide, but I doubt you would ever see those on Step I.

Hope this helps.

Perfect. Thanks so much!! 👍👍