Urea Cycle and Disease

by Kevin Ahern, PhD

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    Now, urea cycle relates to a lot of things in human disease. We've already seen several examples. It is believed to be very underdiagnosed in infant death. And it may represent as much as 20% of all the sudden infant death syndrome deaths that occur. For people who have the non-lethal form, problems can be focused on the accumulation of ammonia or also on citric acid cycle intermediates. And both of those actually occur. So, these tables I'll show in the next two slides depict some of the urea cycle diseases and some of the effects of those. In each case the enzyme I'm describing as deficient is one of the five enzymes that we started with in the feeder reaction or the urea cycle. The carbamoyl phosphate synthethase was the enzyme of the feeder reaction. Deficiency of it leads to the disease carbamoyl phosphate synthethase I deficiency, which the name is pretty much describing exactly what's happening. And the molecule that accumulates in this case is ammonium. The ammonia of course was produced by the catabolism of amino acids. So, if this can't be made into carbamoyl phosphate, ammonia will accumulate. The symptoms of this disease include developmental delay and mental retardation Ornithine transcarbamylase catalyzes that first reaction of the urea cycle. And its name also like the other one is ornithine transcarbamylase deficiency and that also describes exactly what has happened here. The molecules that accumulate with the deficiency of this enzyme include ornithine, uracil and orotic acid. Now, the symptoms of this disease are pretty severe. We're talking about death and seizures in the severe cases. But in adults, if it's an adult onset, there's a very wide spectrum of results and in some cases can actually be managed with diet. The argininosuccinate when it's deficient leads...

    About the Lecture

    The lecture Urea Cycle and Disease by Kevin Ahern, PhD is from the course Amino Acid Metabolism.

    Author of lecture Urea Cycle and Disease

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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