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Hexokinase and glucokinase: Difference between revisions

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Hexokinase and glucokinase (view source)

Revision as of 13:12, 20 May 2023

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(Created page with "Hexokinase is an enzyme which catalyzes the phosphorylation of glucose into glucose 6-phosphate. There are multiple forms, from I to IV. Hexokinase IV is also called glucokinase. Glucokinase (hexokinase IV) differs from the other three types of hexokinase (hexokinase I, II and III) in multiple ways. They’re summarized in the table below. {| class="wikitable" !Property !Hexokinase (I, II, III) !Glucokinase (hexokinase IV) |- |Concentration of glucose where enzyme is ha...")
 
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Inside the hepatocyte will glucokinase rapidly convert glucose into glucose 6-phosphate. If hexokinase would be present instead of glucokinase would the reaction stop very quickly as glucose 6-phosphate accumulates in the cell. However, glucokinase is not inhibited by its product.
Inside the hepatocyte will glucokinase rapidly convert glucose into glucose 6-phosphate. If hexokinase would be present instead of glucokinase would the reaction stop very quickly as glucose 6-phosphate accumulates in the cell. However, glucokinase is not inhibited by its product.


Glucokinase is also saturated at a much higher glucose concentration than hexokinase, so it’s able to keep up with the large amount of glucose, whereas hexokinase would be overwhelmed.
Glucokinase is also saturated at a much higher glucose concentration than hexokinase, so it’s able to keep up with the large amount of glucose, whereas hexokinase would be overwhelmed. In other words, glucokinase has a higher VMAX (maximum reaction rate).


When between meals, blood glucose drops, and the liver does not want to use any of the scarce glucose in the blood, but instead leave it for other organs. Because glucokinase has a high KM it will not be active when blood glucose is low, so the liver doesn’t use up the glucose.
When between meals, blood glucose drops, and the liver does not want to use any of the scarce glucose in the blood, but instead leave it for other organs. Because glucokinase has a high KM it will not be active when blood glucose is low, so the liver doesn’t use up the glucose.