Biology 3602A/B Lecture Notes - Lecture 39: Glutathione Reductase, Unpaired Electron, Glutathione

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5 Aug 2016
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Superoxide has the unpaired electron that makes it very reactive
Peroxide: add another electron to make it very reactive
H2O2 pretty reactive
Hydroxyl radical: quite reactive
OH-: not that reactive
ROS typically have an unpaired e- in outer orbital which makes them unstable
To stabilize outer orbital, they’ll steal e- from other molecs, and when it does that it’ll
damage those molecs
Specifically, you can damage macromolecs like lipids, nucleic acids and proteins – you
can peroxidize them
Animals can systems of detoxifying ROS
Some of them are enzymatic
SOD dismutes superoxides, and turns it from superoxide to H2O2 which is less reactive
but still not great
So can further degrade H2O2 using CAT that converts it into H2O and O2
Also take that H2O2 and use GPx which, using glutathione as a cofactor, produces
water
Glutathione peroxidase reqs reduced glutathione, so glutathione reductase takes
oxidized glutathione and reducing equivs like NADPH to regenerate glutathione
We can also deal with them nonenzymatic – nonenzymatic antioxidants aka free radical
scavengers
These are compounds like vitamins E, and C, etc.
These can accept electrons from ROS w/o becoming toxic themselves; so vitamin C
can accept electron from free radical / ROS, and turns itself into dehydroascorbate
which isn’t toxic
But in the process you’ve gotten rid of the reactive electron of the ROS
Direct damage: UV radiation can damage DNA directly – a photon of UV radiation can
turn thymines into thymine glycols
In healthy DNA, thymine (in yellow) normally binds with adenine; but if you turn
thymines into thymine glycols, they no longer prefer adenine and much rather binds with
other thymine glycols – they’ll bind to themselves
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