Answer:
The catalytic mechanism of glucokinase (GK) is still not fully understood, but it is thought to involve the following steps:
Glucose binds to GK in a specific pocket.
ATP binds to GK in a different pocket.
The two substrates are brought close together by GK.
A general acid-base catalyst in GK deprotonates the C6 hydroxyl group of glucose.
A nucleophilic attack by the C6-hydroxyl group of glucose on the α-phosphate of ATP takes place.
The reaction is completed by the release of ADP and glucose-6-phosphate.
GK is a very efficient catalyst, and it is thought that its efficiency is due to the following factors:
The specific binding of the substrates to GK creates a favorable orientation for the reaction to take place.
The presence of a general acid-base catalyst in GK speeds up the reaction by providing a proton to protonate the C6 hydroxyl group of glucose and a base to abstract a proton from the α-phosphate of ATP.
The close proximity of the substrates in GK allows the reaction to take place more easily.
GK is an important enzyme in the regulation of glucose homeostasis. It is the rate-limiting enzyme in the hepatic phosphorylation of glucose, and it plays a role in the regulation of insulin secretion.
Step-by-step explanation: