Enzymology and Catalytic Mechanism Carbohydrate Metabolism ATP

¶ … Doctor Determine Treatment for a Diagnosis of Hereditary Fructose Intolerance:

Explain how enzymes are involved in processes such as the breakdown of fructose.

The enzymes work as a lock and key process where the relevetn active part of the enzyme fits into the substrate (i.e. The molecule on which the enzyme acts) and activates it. There are various active sites on the enzyme and only the enzyme that will 'fit' in the substrate will work. After part of enzyme matching with substrate, enzyme breaks down substrate into two smaller products.

The following image illustrates:

(adapted from http://waynesword.palomar.edu/molecu1.htm)

At times the process can be blocked by an impediment that stops the 'key' from 'turning, as happens in the case of a lack in aldolase B. which can prompt hereditary fructose intolerance

Explain how a deficiency in aldolase B. can be responsible for hereditary fructose intolerance.

Hereditary fructose intolerance is a disease that disable the individual from consuming sugar fructose. Hereditary fructose intolerance is characterized an autosomal recessive pattern, where each parent of the victim carries a recessive copy of the gene (i..e gene is there but it only comes out in carrier; it is recessive in parent).

The ALDOB gene provides instructions for making the aldolase B. enzyme. This enzyme largely exists in the liver and defuses (i.e. metablizes) the fructose / sugar which is in turn used for energy. The ALDOB gene serves as impediment on enzyme lock and key system in that it prevents the enzyme from effectively tuning into and turning substrate and hinders the ability of the enzyme to metabolize sugar. The lack of healthy aldolase B. results in a mass of fructose phosphates accumulating in the liver which subsequently results in death of liver cells. The weakened operations of the aldolase B. enzyme also produces less dihydroxyacetone phosphate which results in fewer phosphates in the body and also harms the body since altogether, destruction of liver cells and reduced phosphates cause hypoglycemia, liver dysfunction, and other factors of hereditary fructose intolerance. (Genetics Home Ref. Hereditary fructose intolerance http://ghr.nlm.nih.gov/condition/hereditary-fructose-intolerance)

3. Provide clearly labeled diagrams to demonstrate:

a. Diagram lock and key models of enzymatic activity.

b. Diagram the effect of enzymes on activation energy.

4.

With temperature, pressure, concentration, and/or surface area of enzyme increased, the activation energy of the substrate is heightened / intensified. The diagram (retrieved form BioChem Notes http://as-bio-and-chem.blogspot.com/2010/09/recapping-rates-of-reaction-kinetics.html) shows how the peak of activation intensifies impact of product.

4. Discuss the specific substrate acted on by aldolase B.

Aldolese B. metabolizes the glycolytic-gluconeogenic pathway. More specifically, it metabolizes the breakdown of F1P into glyceraldehyde and DHAP (Cross NC, de Franchis R, Sebastio G, et al. (1990).

5. Explain the role of aldolase B. In the breakdown of fructose.

The lack of healthy aldolase B. results in a mass of fructose phosphates accumulating in the liver which subsequently results in death of liver cells. The weakened operations of the aldolase B. enzyme also produces less dihydroxyacetone phosphate which results in fewer phosphates in the body and also harms the body since altogether, destruction of liver cells and reduced phosphates cause hypoglycemia, liver dysfunction, and other factors of hereditary fructose intolerance. (Genetics Home Ref. Hereditary fructose intolerance http://ghr.nlm.nih.gov/condition/hereditary-fructose-intolerance)

A. Case 2 - The doctor suspects mitochondrial disease which can occur at multiple levels in different mitochondrial processes. To help the doctor determine where the defect might have occurred:

1. Explain what would happen to the amount of energy available to a cell if the entire Cori cycle occurred and remained within that single cell (i.e., a muscle cell).

The Cori cycle refers to the metabolic pathway where lactate created by anaerobic glycolysis in the muscles flows to the liver and is converted to glucose, which once again is absorbed by the muscles and is converted back to lactate.

The other half of the Cori cycle occurs where, instead of lactate produced by anaerobic fermentation massing UP inside the muscle cells, the lactate is transferred to the liver where gluconeogenesis occurs. Gluconeogenesis converts lactate into glucose (is supplied to the muscles through the bloodstream) by converting the glucose first into pyruvate. The Cori cycle needs multiple cells for its effectiveness. If it were limited / confined to one cell, the entire process would fail.

2. Construct a dynamic diagram to show the doctor why the citric acid cycle is central to aerobic metabolism.

Note: A dynamic diagram should be clearly labeled and include arrows to show movement and interactions.

The citric acid cycle is the first stage in metabolism which consists of removing high-energy electrons from carbon fuels (left). Those electrons then generate a steep proton high (middle), which creates adenosine triphosphate (ATP )(right). The two together (the entire process / synthesis) creates aerobic metabolism (Berg JM, Tymoczko JL, Stryer L. (2002)).

3. Explain where in the citric acid cycle a hypothetical defect of an enzyme could occur that prevents an increase in adenosine triphosphate (ATP) production in response to an increased energy need and how the products of the citric acid cycle are converted into ATP.

The citric acid cycle generates electrons from carbon fuels. ATP is created by the citric acid cycle extracting the electrons from the coenzyme CoA and using these electrons to create and synthesize NADH and FADH2.