Km in Hexokinase and Glucokinase :

PROPEIES OF TWO ISOENZYMES OF HEXOKINASE Hexokinase Glucokinase (Hexokinase IV) Phosphorylates all hexoses Phospharylates only Glucose Present in all cells Present in liver and pancreas (GLUT-2) High affinity less (s) required active in fasting state low km low Vmax Low affinity, more (s) required, active in fed state high km high Vmax Feedback inhibition by Glucose-6-Phosphate Induced by Insulin (Option-4) - Amount of Glucose ingested will decide which isoezyme will be more active but it does not change the affinity of these enzymes for glucose phosphorylation i.e. Km does not get affected by amount of glucose ingested. Extra Information: Hexokinase Isoenzymes are of 4 types - Type I, Type II, Type III, Type IV Hexokinase II - most abundant, overexpressed in cancerous cells Hexokinase IV - known as Glucokinase