Question

Determine whether each phrase describes glucokinase, hexokinase isozymes I–III, or all hexokinase isozymes. Note: Assume that the kinetic behavior of hexokinase isozymes in vivo is similar to in vitro. Glucokinase (hexokinase IV) Hexokinase I, II, or III All hexokinase isozymes (I–IV)

Answer 1

Glucokinase ( Hexokinase IV): Plays significant role, not sensisitve

Hexokinase I II or III : In tissues,

Step-by-step explanation:

A) Plays a significant role in liver regulation of blood glucse levels. (It is present within liver).

B) It is not sensitive to inhibition by glucose-6-phoaphate(remians active even when glucose is abundant and is not effected by allosteric inhibition.)

C) Subcellular localisation is regulated by fructose-6-phosphate (when fructose -6-phosphate concentration is high causes localisation of hexokinase IV to nucleus as it is inhibited by high Fructose-6-phosphate concentration and releases into cytosol when glucose concntration is high)

2. Hexokinase I II or III :

A)Present in tissues that sense blood glucose levels.

B) When blood glucose levels fall below normal range maintains maximum velocity. ( since it has high affinity for glucose and low glucose concentration favors low Km for hexokinase I II III) .

Answer 2

• Glucokinase (Hexokinase IV):

- Subcellular localization is regulated by frutose 6-phosphate

- present in tissues that sense blood glucose levels

- not sensitive to inhibition by glucose 6-phosphate

- plays an important role in liver regulation of blood glucose level

• Hexokinase I, II, or III

- when blood glucose levels fall below normal range, maintains maximum velocity

- when blood glucose is low, will cause cells to trap glucose by phosphorytation

- wil be saturated by normal blood glucose concentrations

• All hexokinase isozymes (I-IV)

- will phosphorylate several hexoses including glucose