The Structure and Mechanism of Hexokinase: Difference between revisions
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In the pancreas, a rise in glucose levels increases the activity of glucokinase causing an increase in glucose 6-phosphate. This causes the triggering of the beta cells to secret insulin<ref>PMID:11237213</ref>. Glucokinase is the first step in this reaction. Insulin then allows other cells in the body to take up glucose, actively lowering the glucose level | In the pancreas, a rise in glucose levels increases the activity of glucokinase causing an increase in glucose 6-phosphate. This causes the triggering of the beta cells to secret insulin<ref>PMID:11237213</ref>. Glucokinase is the first step in this reaction. Insulin then allows other cells in the body to take up glucose, actively lowering the glucose level | ||
== Active Sites == | |||
The active site residues for Hexokinase are Asp205, Lys169, Asn204, Glu256,and Thr168. These residues are located in the deep cleft at the interface between the two lobes. This active site is capable of bonding two ligands, glucose, and glucose-6-phosphate. Hexokinase undergoes an induced fit conformational change when glucose binds. This conformational change prevents the hydrolysis of ATP, and is allosterically inhibited by physiological concentrations of glucose-6-phosphate the product. Hexokinase has two conformational states. The open state occurs prior to glucose binding. ATP is bound to the large lobe, but is far away from the glucose binding site, and in a different position than it assumes in the active site. When the glucose binds to Hexokinase a large conformational change occurs. This change closes the two lobes around the glucose substrate. This conformational state is referred to as the closed state. | |||
==Additional Resources== | ==Additional Resources== | ||
