What is the substrate for glucokinase?
Glucokinase activity in the cytoplasm rises and falls with available glucose. G6P, the product of glucokinase, is the principal substrate of glycogen synthesis, and glucokinase has a close functional and regulatory association with glycogen synthesis.
What is glucokinase inhibited by?
In the presence of fructose 6-phosphate, the regulatory protein binds to, and inhibits, liver glucokinase. Fructose 1-phosphate antagonizes this inhibition by causing dissociation of the glucokinase-regulatory protein complex.
Why does glucokinase have a high Vmax?
Glucokinase, on the other hand, has a high Km and a High v-max, which allows the liver to effectively remove large amounts of dietary glucose from the blood, and prevents large amounts of glucose from entering systemic circulation following a carbohydrate-rich meal.
Why do glucokinase and hexokinase have different enzyme kinetics?
The difference of glucokinase from the other hexokinases is that glucokinase has a lower affinity, thus a higher Km, for glucose. The reduced affinity for glucose allows the activity of glucokinase to differ under physiological conditions according to the amount of glucose present.
Why does glucokinase have low affinity for glucose?
Due to regulation by GCKR, glucokinase in intact liver cells has a lower affinity for glucose than does the purified enzyme, and low concentrations of fructose stimulate glucose utilization by the liver (Agius, 2016; Van Schaftingen et al., 1994).
Does hexokinase exhibit substrate specificity?
Generally, ATP-dependent hexokinases (ATP-HKs, EC 2.7. ATP-HKs from eukaryotes generally show broad substrate specificity for hexoses including mannose and fructose as well as glucose (4).
How might glucokinase differ kinetically from hexokinase so as to function only at high glucose levels?
Glucokinase is active only when the blood concentration of glucose high. How might glucokinase differ kinetically from hexokinase so as to function only at high glucose levels? Glucokinase has a higher Km Value which allows the enzyme to become more active at high glucose concentration, when hexokinase is saturated.
Is Fructokinase a substrate specific enzyme?
The enzyme specifically phosphorylated fructose. The use of the enzyme as an analytical reagent was also investigated. enzymes, however, has broad substrate specificities; i.e., glucose and/or mannose were phosphorylated by these enzymes. In various fields a true fructokinase (highly specific enzyme) is needed.
How is glucokinase regulated in the liver?
Glucokinase expression is transcriptionally regulated by hormones and metabolites of glucose, and glucokinase activity is dependent on reversible binding of glucokinase to a specific inhibitor protein, glucokinase regulatory protein (GKRP), and to other binding proteins such as 6-phosphofructo-2-kinase/fructose 2,6- …
What is the Vmax of glucokinase?
The maximum reaction rate (Vmax) of glucokinase is quite high, resulting in a rapid conversion of glucose into usable energy. Glucokinase comes into play following a large meal, or an influx of carbohydrates, which is related to the control mechanism for this particular enzyme.