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Hexokinase IV is present in the liver, pancreas, hypothalamus, small intestine, and perhaps certain other neuroendocrine cells, and plays an important regulatory role in carbohydrate metabolism. In the β cells of the pancreatic islets, it serves as a glucose sensor to control insulin release, and similarly controls glucagon release in the α ...
The glucokinase regulatory protein (GKRP) also known as glucokinase (hexokinase 4) regulator (GCKR) is a protein produced in hepatocytes (liver cells). GKRP binds and moves glucokinase (GK), thereby controlling both activity and intracellular location [1] [2] of this key enzyme of glucose metabolism. [3] GKRP is a 68 kD protein of 626 amino acids.
Hexokinase III, also known as hexokinase C, is an enzyme which in humans is encoded by the Hk3 gene on chromosome 5. [ 5 ] [ 6 ] Hexokinases phosphorylate glucose to produce glucose-6-phosphate , the first step in most glucose metabolism pathways.
At this step, glycolysis has reached the break-even point: 2 molecules of ATP were consumed, and 2 new molecules have now been synthesized. This step, one of the two substrate-level phosphorylation steps, requires ADP; thus, when the cell has plenty of ATP (and little ADP), this reaction does not occur. Because ATP decays relatively quickly ...
Hexokinase II, also known as Hexokinase B and HK2, is an enzyme which in humans is encoded by the HK2 gene on chromosome 2. [5] [6] Hexokinases phosphorylate glucose to produce glucose 6-phosphate, the first step in most glucose metabolism pathways. Hexokinase II is the predominant hexokinase form found in skeletal muscle.
Hexokinase I, also known as hexokinase A and HK1, is an enzyme that in humans is encoded by the HK1 gene on chromosome 10. Hexokinases phosphorylate glucose to produce glucose-6-phosphate (G6P), the first step in most glucose metabolism pathways. This gene encodes a ubiquitous form of hexokinase which localizes to the outer membrane of ...
Hexokinase can return the molecule to the glycolysis pathway by phosphorylating fructose to form fructose-6-phosphate. However, in uncontrolled diabetics that have high blood glucose - more than the glycolysis pathway can handle - the reactions mass balance ultimately favors the production of sorbitol. [6]
These features allow it to regulate a "supply-driven" metabolic pathway. That is, the rate of reaction is driven by the supply of glucose, not by the demand for end products. [14] Because of the cooperativity, the kinetic interaction of glucokinase with glucose does not follow classical Michaelis-Menten kinetics.