Hexokinase and glucokinase both catalyze the first reaction of glycolysis. $$\text{glucose + ATP} \xrightarrow [ ]{ } \text{glucosephosphate + ADP}$$ The. Regulation of glucokinase by sequestration in the nucleus. Note the sigmoidicity for glucokinase and the much lower Km for hexokinase I. When blood. Glucokinase: Km = 10 mM, not inhibited by glucose 6-phosphate. Present in liver and in pancreas b cells. Hexokinase: Km= mM, inhibited by glucose 6-phosphate. Present in most cells.


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Cells have the enzymes according to their unique functions and the best example of this phenomenon is presence of hexokinase and glucokinase enzymes.

  • Anomeric specificity of hexokinase and glucokinase activities in liver and insulin-producing cells.
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ATP participates in the reaction in a form complexed to magnesium Mg as a cofactor. Furthermore, glucokinase and hexokinase certain conditions, glucokinase, like other hexokinases, can induce phosphorylation of glucokinase and hexokinase hexoses 6 carbon sugars and similar molecules.

Therefore, the general glucokinase reaction is more accurately described as: Glucokinase has a lower affinity for glucose than the other hexokinases.


That is, the rate of reaction is driven by the supply of glucose, not by the demand for end products. Another distinctive property of glucokinase is its moderate cooperativity with glucose, with a Hill coefficient nH of about glucokinase and hexokinase.

BiologyGuide: A-Level Biology Revision Notes

The velocity of the reaction catalysed by liver glucokinase was higher with with beta- than with alpha-D-glucose, whatever the glucose concentration. Remember where the enzymes of glycolysis are found within the cell! Hexokinase This enzyme is involved in the conversion of glucose into glucosephosphate G6P.

This helps the cell to maintain a diffusion glucokinase and hexokinase into the cell at high blood glucose concentrations and glucokinase and hexokinase the diffusion out of the cell at low blood glucose concentrations.

Glucokinase - Wikipedia

There are 3 different types of this enzyme. Hexokinase I-III are found in most tissues of the body, while hexokine IV called glucokinase is found within the liver.

The difference between glucokinase and hexokinase I-III is that glucokinase only works at high glucose concentrations. When blood glucose levels are high, most tissues including brain and muscles will have enough glucose available for uptake.

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As the blood glucose levels have to return to normal glucokinase and hexokinase remember homeostasisthe liver takes up the excess glucose by using glucokinase. When blood glucose levels are low, most tissues, especially the brain, require glucose for respiration, may it be anaerobic or aerobic.

There is a lot of glucose stored in the liver, therefore the liver does not need to take up any glucose during starvation. Instead, the liver glucokinase is inhibited as it only works in high concentrations and glucose is left for the brain and other tissues to allow them to continue with glucokinase and hexokinase work.

Anomeric specificity of hexokinase and glucokinase activities in liver and insulin-producing cells.

During starvation, glucokinase and hexokinase liver also releases glucose by gluconeogenesis the reverse of glycolysis. The glucose can then be released without being taken up again by the glucokinase enzyme.

Type I-III hexokinase are regulated by allosteric inhibition.

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