How Enzymes Work and Breakdown Products

How Enzymes work and breakdown products

Enzymes are proteins that function as catalysts. They are involved in speeding up certain chemical reactions that would be much slower without them. The process or reaction usually is part of a cycle, with separate reactions at each step. This reaction or process cannot be complete without a specific enzyme catalyze. If the cycle is incomplete and there is a lack of product, the function for the organism cannot be performed which negatively affects that organism. Without enzymes the reactions needed for the biological processes of the body would happen at a much slower rate or not at all.

One example of enzymatic action is in the breakdown of fructose. Fructose is a simple sugar found in some of the foods we eat such as fruits and honey. It is a carbohydrate and can be a great source of energy for the body. However, fructose is not a direct energy source for the body and enzymes are needed to breakdown this sugar into usable energy. When eaten, the initial catabolism of fructose is sometimes referred to as fructolysis. This is a cycle that begins with the enzyme fructokinase (usually found in the liver) which produces the product fructose 1-phosphate. Step 2 of this cycle is produced by the enzyme aldolase B which splits the fructose 1-phosphate into dihydroxyacetone phosphate (DHAP) and glyceraldehyde. These two products are able to enter glycolysis to respond to the body’s need for energy or more glucose. Without these enzymes to breakdown fructose, the body would respond very poorly with repeated ingestion of foods containing fructose.

Deficiency in Adolase B

Hereditary fructose intolerance is a condition that affects a person’s ability to digest the sugar found in fructose. This occurs when the body lacks the enzyme aldolase B needed to break down fructose. It is a recessive inherited autosomal disorder that occurs approximately 1 in every 20,000 births (Fernandez, 2006). Genetic mutations in the aldolase B, fructose-bisphosphate (ALDOB) gene is a known cause of heriditary fructose intolerance (HFI). ALDOB provides the genetic code for making the aldolase B enzyme needed to metabolize fructose. One of the genetic mutations that causes a defect in aldolase B is found in position 149 of its polypeptide chain. Normally this position has the amino acid alanine, but the mutation replaces this amino acid with proline (GHR, 2011). This mutation changes the 3-dimensional shape of the enzyme. This alteration in the shape makes it difficult for the enzyme to bind together and form tetramers. If aldolase B is not in a tetramer, it will not be able to metabolize fructose (GHR, 2011).

A.3.a. Lock and Key Enzymatic Activity

Enzymes function to lower the activation energy by temporarily combining with the reactants, which are referred to as substrates. The substrate