Multiple Choice
In the context of phosphorylation, what is the primary function of a protein kinase?
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7. Enzyme Inhibition and Regulation
Phosphorylation
Multiple Choice
In the context of phosphorylation, how do protein kinases most directly affect the activity of enzymes?
A
They catalyze peptide bond hydrolysis, permanently inactivating the enzyme by proteolysis.
B
They increase transcription of the enzyme’s gene by binding directly to promoter DNA sequences.
C
They transfer a phosphate group from to specific amino acid residues on the enzyme, which can alter the enzyme’s conformation and activity.
D
They remove phosphate groups from serine, threonine, or tyrosine residues, thereby reversing enzyme activation.
Verified step by step guidance1
Understand that protein kinases are enzymes that modify other proteins by chemically adding phosphate groups to them, a process known as phosphorylation.
Recognize that the phosphate group donor in this reaction is typically ATP (adenosine triphosphate), which provides the phosphate group that the kinase transfers.
Identify the specific amino acid residues on the target enzyme where phosphorylation occurs, commonly serine, threonine, or tyrosine residues.
Know that the addition of a phosphate group can induce a conformational change in the enzyme, which can either activate or inhibit its activity depending on the context.
Distinguish this action from other processes such as proteolysis (protein degradation), transcriptional regulation, or dephosphorylation, which are not the direct effects of protein kinases.
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