Question

1. XXXXXXXXXXXXXXXXXXXA doctor from Cairo, Egypt is perplexed by two twin infants that he is treating for deficiencies in energy production.   He has many theories on what could be the issue, but he wants you to help. He presented their case to your lab. You sequence these infants DNA and try to uncover what metabolic problem they may have that is causing this energy-deficient illness they have.

1. (10 points) You characterize the enzymes for glycolysis, PDH, and TCA cycle and everything seems fine, except for one thing: you discover that these infants have a very strange pathway never discovered before. This pathway takes oxaloacetate from the body and branches it into a pathway that breaks it in down into seemingly non-biologically relevant intermediates. Why could this explain the energy deficiency the Egyptian doctor discovered? (50 words max).

ANSWER:

                                                  

2. (10 points) You discover that the enzyme that controls this weird oxaloacetate pathway is very similar to Pyruvate Dehydrogenase. Additionally, this pathway can be regulated by reversible covalent modification very similar to that of PDH. These infants have a problem with this regulation, but if this regulation was normal, how could you regulate this weird pathway to solve their problem? Make sure you address ALL possible ways you can regulate, with the knowledge that this is very similar to PDH. (50 words max)

ANSWER:

3. (8 points) You also discover another problem in the infants: a key enzyme responsible for the production of Coenzyme Q (i.e. Ubiquinone) is hugely mutated to work very, very slowly.   This causes very low levels of Coenzyme Q in the infants. Why could this also explain their energy-production problem? (40 words max).

ANSWER:

4. (8 points) You email the doctor and he asks if it is possible to just add Coenzyme Q in the diet if the infant twins. Why may this work, in theory, but why might this be a problem to actually do in the body? Consider the structure of Coenzyme Q and where it is located in the mitochondria? (30 words max).

ANSWER:

Answer 1

A. Oxaloacetate is very important in TCA cycle. Acetyl CoA combines with Oxaloacetate to form citric acid, This is the first step in TCA cycle. So Oxaloacetate has to be present for the TCA cycle to go on in the mitochondria. No TCA and hence ETC also can't produce sufficient ATP molecules. That is why there is lack of energy.

B. Pyruvate dehydrogenase path way is regulated by reversible modification of PDH. It is brought by various kinases. Pyruvate dehydrogenase kinase inactivates PDH by phosphorylation with ATP. It will reactivate by Pyruvate dehydrogenase phosphatase.

PDH kinase is stimulated by NADH and Acetyl CoA , where as inhibited by Pyruvate. Because the weired path way is similar to PDH, it can be regulated by using kinases similar to PDH which will inhibit the path way of Oxaloacetate.

C. Coenzyme -Q is very important because it is an important mobile carrier in electron transport chain. It carrier electrons from complex I and II to complex III. Lack of this mobile carrier will prevent ATP formation. That is why the energy is less in the twins.

D. Co enzyme Q is present int e ETC which is located in the inner mitochondrial membrane. Mostly Coenzyme Q is synthesised in the body with tyrosine. That is why by just adding foods rich in Coenzyme Q will not increase the energy levels of the twins.