Suppose that a protein tyrosine kinase (E) catalyzes a reaction with the kinetic
ID: 7254 • Letter: S
Question
Suppose that a protein tyrosine kinase (E) catalyzes a reaction with the kinetic mechanism shown below, in which a phosphate group from ATP is transferred to a Tyr residue on the target protein.
key to below diagram:
1. * represents applying to word below it. For example the first one states ATP enters in
2. # represents a bond between the two.
3. E represents the word enzyme
4. P represents the word protein
5. P2 represents protein-OPO3^-2
6. (X)= E#ATP#target Protein and (Y)= E#ADP#targetP2
7. _______ represents the route of the reaction
Part 1
(*enters in) (*enters in)
__ATP___________Target Protein_________________
E E#ATP (X) ---> (Y)
<---
Part 2
Target P2_________ADP____________
E#ADP E
The protein kinase activity can be assayed by phosphorylation of a small peptide substrate containing
the consensus specificity sequence from the target protein that includes the Tyr residue.
A. How would you describe the kinetic mechanism of this protein kinase?
B. Write the general reaction by which a cell would remove the phosphate group from the target
protein. What enzyme(s) catalyze this process?
Explanation / Answer
A.The kinetic mechanism of this protein kinase can be written in this way:
The enzyme first binds an ATP molecule. Then this Enzyme-ATP complex reacts with the target protein and transfers one phosphate group to the protein. In this way,enzyme-ATP is converted to enzyme-ADP.
B. Target protein + ADP ---> target protein + phosphate+ATP
The enzyme which catalyzes this processes are phosphatases
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