glucokinase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: ATP + D-glucose = ADP + D-glucose-6-phosphate. [EC:2.7.1.2]

Glucokinase activity is a critical enzyme involved in the first committed step of glucose metabolism. It catalyzes the phosphorylation of glucose to glucose-6-phosphate (G6P), utilizing ATP as a phosphate donor. This reaction is essential for glucose entry into glycolysis, the primary pathway for glucose breakdown to generate energy.

Glucokinase exhibits distinct kinetic properties compared to other hexokinases, displaying a lower affinity for glucose but a higher capacity for glucose phosphorylation at high glucose concentrations. This allows glucokinase to function as a glucose sensor in the liver and pancreatic β-cells, playing a vital role in regulating insulin secretion and hepatic glucose homeostasis.

Specifically, in pancreatic β-cells, glucokinase activity is crucial for glucose-stimulated insulin secretion (GSIS). As blood glucose levels rise, increased glucose uptake by β-cells leads to elevated glucokinase activity. The resulting increase in G6P levels stimulates a signaling cascade that ultimately leads to insulin release. This mechanism ensures that insulin secretion is tightly regulated by blood glucose levels, preventing hyperglycemia.

In the liver, glucokinase plays a significant role in regulating hepatic glucose production and storage. When blood glucose levels are high, glucokinase activity promotes glucose uptake and conversion to glycogen, the storage form of glucose. Conversely, when blood glucose levels are low, glucokinase activity is reduced, allowing the liver to release glucose into the bloodstream to maintain blood glucose homeostasis.

Furthermore, glucokinase exhibits tissue-specific expression patterns. While it is highly expressed in the liver and pancreatic β-cells, its expression is much lower in other tissues. This selective expression further emphasizes its critical role in regulating glucose metabolism in these specific organs.

In summary, glucokinase activity is an essential enzyme that plays a crucial role in glucose metabolism by catalyzing the phosphorylation of glucose to G6P. Its unique kinetic properties and tissue-specific expression patterns make it a key regulator of glucose homeostasis, insulin secretion, and hepatic glucose production and storage.'
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Proteins (4)

Compounds (9)