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Once glucose enters the cell, the first step is phosphorylation of glucose by a family of enzymes called hexokinases to form glucose 6-phosphate (G6P). This reaction consumes ATP, but it acts to keep the glucose concentration inside the cell low, promoting continuous transport of blood glucose into the cell through the plasma membrane transporters.
Glucose 6-phosphatase can convert glucose 6-phosphate back into glucose exclusively in the liver, so the body can maintain a sufficient blood glucose concentration. In other cells, uptake happens by passive transport through one of the 14 GLUT proteins. [ 80 ]
First, glucose metabolism is faster through ethanol fermentation because it involves fewer enzymes and limits all reactions to the cytoplasm. Second, ethanol has bactericidal activity by causing damage to the cell membrane and protein denaturing , allowing yeast fungus to outcompete environmental bacteria for resources. [ 6 ]
Hence, an abundance of F6P results in a higher concentration of fructose 2,6-bisphosphate (F-2,6-BP). The binding of F-2,6-BP increases the affinity of PFK1 for F6P and diminishes the inhibitory effect of ATP. This is an example of feedforward stimulation as glycolysis is accelerated when glucose is abundant. [3]
Glucose oxidase enzyme powder from Aspergillus niger. GOx is a dimeric protein, the 3D structure of which has been elucidated. The active site where glucose binds is in a deep pocket. The enzyme, like many proteins that act outside of cells, is covered with carbohydrate chains. GOx is a glucose oxidising enzyme with a molecular weight of 160 kDa.
In biochemistry, denaturation is a process in which proteins or nucleic acids lose folded structure present in their native state due to various factors, including application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), agitation and radiation, or heat. [3]
For example, hexokinase, the first enzyme in the glycolysis pathway, has a specialized form called glucokinase expressed in the liver and pancreas that has a lower affinity for glucose yet is more sensitive to glucose concentration. [99] This enzyme is involved in sensing blood sugar and regulating insulin production. [100]
Ball-and-stick model of a glucose molecule. Blood sugar regulation is the process by which the levels of blood sugar, the common name for glucose dissolved in blood plasma, are maintained by the body within a narrow range. The regulation of glucose levels through Homeostasis. This tight regulation is referred to as glucose homeostasis.