The fourth step in glycolysis employs an enzyme, aldolase, to cleave 1,6-bisphosphate into two three-carbon isomers: dihydroxyacetone-phosphate and glyceraldehyde-3-phosphate. The newly added high-energy phosphates further destabilize fructose-1,6-bisphosphate. This is a type of end product inhibition, since ATP is the end product of glucose catabolism. Thus, if there is “sufficient” ATP in the system, the pathway slows down. It is active when the concentration of ADP is high it is less active when ADP levels are low and the concentration of ATP is high. In this pathway, phosphofructokinase is a rate-limiting enzyme. A second ATP molecule donates a high-energy phosphate to fructose-6-phosphate, producing fructose-1,6-bisphosphate. The third step is the phosphorylation of fructose-6-phosphate, catalyzed by the enzyme phosphofructokinase. This change from phosphoglucose to phosphofructose allows the eventual split of the sugar into two three-carbon molecules. An isomerase is an enzyme that catalyzes the conversion of a molecule into one of its isomers. In the second step of glycolysis, an isomerase converts glucose-6-phosphate into one of its isomers, fructose-6-phosphate. This reaction prevents the phosphorylated glucose molecule from continuing to interact with the GLUT proteins, and it can no longer leave the cell because the negatively charged phosphate will not allow it to cross the hydrophobic interior of the plasma membrane. Hexokinase phosphorylates glucose using ATP as the source of the phosphate, producing glucose-6-phosphate, a more reactive form of glucose. The first step in glycolysis is catalyzed by hexokinase, an enzyme with broad specificity that catalyzes the phosphorylation of six-carbon sugars. The first half of glycolysis uses two ATP molecules in the phosphorylation of glucose, which is then split into two three-carbon molecules. Lactic acidosis can lead to serious health problems such as coma and death.Figure 2. ![]() Lactic acidosis can be caused by problems with the enzymes that are involved in glycolysis or by a lack of oxygen. Overactive glycolysis can lead to lactic acidosis, which is a build-up of lactate in the blood. Cancer cells often rely on glycolysis for energy because the Warburg effect allows them to bypass oxidative phosphorylation.ĭiseases caused due to overactive glycolytic pathway are less common, but they can be very serious. The glycolysis pathway is important for the survival of tumor cells. Defects in pyruvate kinase can also lead to heart disease. Diseases that can be caused by problems with glycolysis include diabetes, cancer, and heart disease.ĭeficiency in glycolytic enzymes such as hexokinase can lead to diabetes. ATP is essential for cellular function, and problems with its production can lead to symptoms such as weakness, fatigue, and muscle pain. This means that there is a net production of two ATP in glycolysis.ĭysfunctional glycolysis can lead to problems with the production of energy. However, four molecules of ATP are produced as a result of this pathway. In glycolysis, two molecules of ATP are used to convert glucose into energy. ATP is produced as a result of the transfer of phosphate groups from glucose-phosphate to ADP.
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