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Carbamoyl Phosphate Synthetase Reaction and Citrulline

by Kevin Ahern, PhD
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    So I've now gone through the cycle as a whole. What I want to do now is focus in a little bit more closely on each of the enzymes that I've been talking about. The first enzyme of course is carbamoyl phosphate synthetase. Now, this reaction requires ammonium ion. And the ammonium ion in this reaction is ultimately coming from glutamine or glutamate. These may have gotten their ammine from another amino acid. The reaction requires the action of either glutaminase in the case of breaking down glutamine to make ammonium ion or glutamate dehydrogenase which breaks down glutamate to get that ammonium ion. We see these reactions here. It's a hydrolysis in the case of glutamine to release and produce glutamate plus that ammonium, or it's also hydrolysis in the case of glutamate that produces alpha-ketoglutarate and the ammonium ion as we see here. In the case of the glutamate dehydrogenase that's an oxidation as the name dehydrogenase would suggest and the electrons are donated to NADP to make NAPH. So, we have produced the ammonia or ammonium ion necessary for the reaction I've described. The production of the bicarbonate is done very easily within the cell and I won't go into that right here. We thus have the bicarbonate and the ammonium that we need for the reaction catalyzed by the carbamoyl of phosphate synthethase and we see that happening right here coming either from the glutamine side or from the glutamate side. The net result is that we have made the carbamoyl phosphate necessary for the feeder reaction. The ornithine transcarbamoylase reaction is shown here. In this reaction, we see of course carbomyl phosphate combines with ornithine to make citrulline with the release of a phosphate. The enzyme is of course ornithine transcarbamoylase. The enzyme is expressed...

    About the Lecture

    The lecture Carbamoyl Phosphate Synthetase Reaction and Citrulline by Kevin Ahern, PhD is from the course Amino Acid Metabolism.


    Included Quiz Questions

    1. It catalyzes the formation of citrulline.
    2. It catalyzes the formation of ornithine.
    3. It requires ATP.
    4. All of the answers are true.
    5. None of the answers are true.
    1. Nitric oxide synthase can be used.
    2. Arginine is produced.
    3. Nitric oxide is required.
    4. All of the answers are true.
    5. None of the answers are true.

    Author of lecture Carbamoyl Phosphate Synthetase Reaction and Citrulline

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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