Ls4203_class test_2017 5. Liver contain both Hexokinase and Glucokinase: catalyze reaction(i.e. glucose + ATP -> glucose-6-phosphate...

Ls4203_class test_2017

5. Liver contain both Hexokinase and Glucokinase: catalyze reaction(i.e. glucose + ATP -> glucose-6-phosphate + ADP). Describe how glucokinase and hexokinase regulate blood glucose homeostasis? How activity of hexokinase and glucokinase is regulated? (3+2=5 marks)

Expert Solution

Glucokinase is a type of hexokinase. Hexokinases are of 4 types (I , II, III, IV), of which glucokinase is hexokinases IV which is specifically acts on glucose (as opposed to any 6-carbon sugar in case of the other 3 hexokinases) and is found in liver. Hexokinases I and III is found in all cells while II is found in heart and muscles. Hexokinases I, II, III have a higher Km as compared to glucokinase (hexokinase IV). All of them are allosterically regulated by their phosphorylated substrates.

Hence when blood glucose levels are high, and so are the intracellular glucose -6- phosphate levels, hexokinase I,II and III are shut down while hexokinase IV is still active and takes up and metabolizes the glucose thereby lowering the blood glucose levels. When blood glucose levels are down, glucose-6-phosphate in the cells is less too,hexokinase I,II,III are un-inhibited and glucose is metabolised but hexokinase IV is off

gladiator answered 1 year ago

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