Hexokinase Vs Glucokinase || Medical Biochemistry By Dr Prakash Mungli

📌𝐅𝐨𝐥𝐥𝐨𝐰 𝐨𝐧 𝐈𝐧𝐬𝐭𝐚𝐠𝐫𝐚𝐦 :-   / drgbhanuprakash  

Glucokinase and Hexokinase are enzymes which phosphorylate glucose to glucose-6-phosphate, trapping glucose inside the cell.

HEXOKINASE (I, II & III) vs. GLUCOKINASE (IV)

Tissue distribution
------------------------------
Hexokinase
Skeletal muscle (most common example even though it occurs throughout most of the body)

Glucokinase
The liver
The pancreas (its beta cells)
Less notably, also in select cells of the intestine and brain.

Kinetics (Km and Vmax)
--------------------------------------
Hexokinase
lower Km
lower Vmax
at fasting glucose levels, hexokinase is at Vmax

Glucokinase
high Km -- spares glucose stores for hexokinase in the brain, muscle and other tissues
high Vmax
glucose sensor -- at fasting glucose levels, glucokinase activity varies according to blood glucose concentration

Regulation (allosteric vs hormonal)
--------------------------------------------------------
Hexokinase (allosteric regulation)
allosterically inhibited by glucose-6-phosphate

Glucokinase (hormonal regulation)
inhibited by glucagon
activated by insulin
inactive when bound to glucokinase regulatory protein (GKRP)

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