Case 1 - Hereditary Fructose Intolerance
1 & 2. Enzymes take on a variety of roles in the human body at the cellular level. Specifically, they aid in the breakdown of macronutrients such as glucose and fructose so that the body can use them. Although reactions within the body would occur without enzymes, enzymes provide control because the reaction is not needed all of the time. Enzymes function in specific environments such as temperature or pH; some enzymes are specific in their shape and only promote (or inhibit) a reaction if they combine with their specific substrate - for example, the lock and key model of enzyme/substrate specificity. The Induced Fit Model (see diagram) also explains that the lock and key model does not have to be exact depending on the enzyme and substrate. There is "wiggle room" which allows the two components to adjust to each other, similar to a pair of shoes that has "worn in" and become more comfortable.
Glycolysis is the cellular process of breaking glucose down into energy. In one of the initial stages of the process, glucose is broken down into fructose-6-phosphate, a deficiency in aldolase B stops the process. In the case of Hereditary Fructose Intolerance (HFI) the patient has a deficiency in the generic fructose 1-bisphosphate aldolase enzyme which is expressed in the liver. The lack of aldolase B causes build up of fructose-1-phosphate in the liver and renal structures, which in turn stops glycogen breakdown and stops glucose synthesis. Several foods contain fructose-1-phosphate which is why the ingested foods cause a problem for individuals with HFI.
Fructose metabolism has two initial unique steps before the products can enter the glycolysis process. In the first step, fructose is broken down into fructose - 1 - phosphate by fructokinase. Next, fructose - 1 - phosphate is broken down into DHAP + glyceraldehyde by aldolase B. In HFI, aldolase B does not work or the patient is...
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