Why hexokinase and glucokinase have very different enzyme kinetics?

Hexokinase has a high affinity towards glucose while glucokinase has a low affinity towards glucose. Therefore, hexokinase helps in glycolysis in normal cells while glucokinase facilitates glycogenesis in the liver. The main difference between hexokinase and glucokinase is the cellular localization and the role.

Why does hexokinase have a lower Km than glucokinase?

Hexokinase had lower km value for glucose than glucokinase; i.e. hexokinase has more affinity for glucose than glucokinase.

Is glucokinase the same as hexokinase?

Glucokinase (GK) is a hexokinase isozyme, related homologously to at least three other hexokinases. All of the hexokinases can mediate phosphorylation of glucose to glucose-6-phosphate (G6P), which is the first step of both glycogen synthesis and glycolysis.

Is hexokinase same as glucokinase?

Hexokinase is actually a broader term for a class of enzymes that phosphorylates six-carbon sugars (glucose, fructose, galactose etc.), while glucokinase is a specific type of hexokinase (an isoform) that has a lower affinity for substrates.

Are hexokinase and glucokinase isozymes?

Glucokinase (hexokinase D) is a monomeric cytoplasmic enzyme found in the liver and pancreas that serves to regulate glucose levels in these organs. Glucokinase is a hexokinase isoenzyme.

How are hexokinase and glucokinase regulated?

Hexokinase is allosterically regulated by one of its products (glucose-6-phosphate), whereas glucokinase is hormonally controlled by insulin. When insulin levels rise in the body, glucokinase transcription and activity both increase within an hour.

Why does fructose 6 phosphate inhibit glucokinase?

In the presence of fructose 6-phosphate, the regulatory protein binds to, and inhibits, liver glucokinase. Both phosphate esters act by binding to the regulatory protein, and by presumably causing changes in its conformation. The regulatory protein behaves as a fully competitive inhibitor.

What is the difference between hexokinase and glucokinase?

Unlike hexokinase, which is present in all tissues, glucokinase is only present in liver and pancreatic beta cells, and is akin to a functional control mechanism within the body. The affinity of glucokinase towards glucose is low, meaning that it is only activated when there is an abundance of glucose available to a cell.

What is the function of glucokinase?

What is Glucokinase. Glucokinase is a type of hexokinase only found inside the liver cells and β-pancreatic cells. They have a vital role in carbohydrate metabolism. It is also called hexokinase IV or hexokinase D and encoded by the GCK gene on the chromosome 7 in humans.

Can hexokinase handle a high Vmax?

If there is only a limited amount of glucose, such as during a fasting or resting period, then hexokinase can handle the enzymatic load. The maximum reaction rate (Vmax) of glucokinase is quite high, resulting in a rapid conversion of glucose into usable energy.

What is the substrate of glucokinase IV?

It is also called hexokinase IV or hexokinase D and encoded by the GCK gene on the chromosome 7 in humans. The only substrate of glucokinase is D-glucose and the enzyme is only functional at high glucose levels since it has a low affinity towards glucose.