Both Hexokinase and Glucokinase are enzymes catalyzing the phophorylation of Glucose to Glucose-6-phosphate using ATP. During the reaction, one ATP molecule is cleaved to ADP and the phosphate thus released is added to glucose. Hexokinase and Glucokinae are isoenzymes with same catalytic activity but have different physical properties and site of action. Glucokinase is also called as human hexokinase IV, hexokinase D etc
10 Difference Hexokinase vs Glucokinase
Glucokinase (Hexokinase D)
Present in all tissues except the liver and the Beta cells of pancreas
Present in liver and Beta cells of pancreas
Acts upon many hexoses such as fructose, galactose including glucose
The only substrate is D-glucose
Hexokinase is one of the regulatory enzymes of glycolysis
Glucokinase plays a central role as a glucose sensor in the regulation of glucose homeostasis.
Hexokinase has high Km value that is high affinity for the substrate glucose
Glucokinase has high Km value that means low affinity for the substrate
The maximum reaction rate (Vmax) of hexokinase is low that means it gets saturated quickly by increasing glucose concentration
The maximum reaction rate (Vmax) of glucokinase is quite high, thus can handle larger glucose load resulting in a rapid conversion of glucose into usable energy.
Hexokinase is active even at low glucose levels
Glucokinase is active only at high glucose levels in liver
Is not inducible (*constitutive enzyme)
Is induced by glucose and insulin
Hexokinase is an allosteric enzyme with **allosteric site for regulation of enzyme activity
Glucokinase is not an allosteric enzyme
Feedback inhibition of hexokinase by
glucose 6 phosphate (product)
No direct feedback inhibition; not inhibited by glucose-6-phosphate
*Constitutive enzymes are always produced in constant amounts without regard to the physiological demand or the concentration of the substrate.
**Allosteric site: is the site other than the active site where effector molecule binds and regulated enzyme activity. This type of regulation is called allosteric regulation.

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