Case 1: Hereditary fructose intolerance
Enzymes are proteins that increase the rate of chemical activity. Their three dimensional structure determines their function, and is made of chains of amino acids that have folded into a specific shape with a unique property. Enzymes lower the activation energy needed for a chemical reaction, therefore speeding up the process. Multiple enzymes work together in metabolic pathways, taking a product (end result) of one metabolic reaction as a substrate (substance or molecule at start of process) for another reaction. Metabolic pathways create the avenue for fructolysis, the breakdown (catabolism) of fructose, occurring in the liver, and in muscle and fat tissue. Most of fructose obtained by diet is metabolized in the liver, where the enzyme fructokinase is abundant. This enzyme phosphorylates the substrate (fructose) into fructose-1-phosphate, which is then split into glyceraldehyde and dihydroxyacetone phosphate, both three carbon molecules that can enter the glycolytic pathway for further oxidation and energy production. Enzymes are specific to a substrate, meaning they have an active spot on the enzyme that will only work with a specific shape of a particular substance (substrate). Aldolase B deficiency
Aldolase B is an enzyme found predominantly in the liver that plays a major role in fructose metabolism. In hereditary fructose intolerance (HFI), individuals have a build up of fructose 1- phosphate (F1P), due to the absence or deficiency of aldolaseB, necessary to break down F1P into the two three carbon molecules utilized in the glycolytic pathway. The F1P is toxic to cells and tissues in the body, causing phosphate to become unusable, and depleting phosphate storage and energy. The decreasing phosphate levels cause glycogenolysis in the liver to halt, affecting blood sugar levels. Persons with HFI can exhibit symptoms of vomiting, trembling, nausea, lethargy, hypoglycemia, hepatomegaly (enlarged liver),...
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