Protein Covalent Modification: Phosphorylation and More

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Questions and Answers

What is the primary function of enzymes in the body?

To catalyze the breakdown of peptides

To synthesize ATP

To regulate the rate of metabolic pathways (correct)

To activate protein phosphatases

What type of modification affects the activity of an enzyme?

Allosteric modification

Covalent modification (correct)

Hydrolysis

Denaturation

What is the effect of ATP buildup on PFK1 enzyme activity?

It increases the substrate concentration

It activates PFK1

It inhibits PFK1 (correct)

It has no effect on PFK1

What is the role of allosteric activators in enzyme regulation?

To bind to the allosteric site and regulate the enzyme through conformational changes Signup and view all the answers

What is the result of ADP binding to the allosteric site of PFK1?

Activation of PFK1 Signup and view all the answers

Which of the following is NOT a characteristic of the R state of an enzyme?

High affinity for allosteric inhibitors Signup and view all the answers

What is the effect of AMP on PFK1 enzyme activity?

It activates PFK1 Signup and view all the answers

What is the purpose of allosteric regulation in enzyme activity?

To prevent simultaneous occurrence of glycolysis and gluconeogenesis Signup and view all the answers

What is the primary function of a protein phosphatase in the context of phosphorylation?

To remove a phosphate by hydrolysis Signup and view all the answers

What is the term for the process by which an inactive enzyme, or zymogen, becomes active?

Proteolysis Signup and view all the answers

What type of post-translational modification adds a phosphate group to a protein?

Phosphorylation Signup and view all the answers

What is the effect of phosphorylation on the activity of an enzyme?

It can either activate or inhibit the enzyme, depending on the context Signup and view all the answers

What is the purpose of making enzymes in an inactive form, known as zymogens?

To prevent the enzyme from prematurely breaking down other proteins Signup and view all the answers

What type of bond can a phosphoryl group make?

Hydrogen bond Signup and view all the answers

What is the net effect of phosphorylation on the charge of a protein?

It adds a negative charge Signup and view all the answers

What is the molecule that provides the phosphate group for phosphorylation?

ATP Signup and view all the answers

What is the function of JAK kinases in JAK-STAT receptors?

Phosphorylate each other in the heterodimer Signup and view all the answers

What is the consequence of misfolded proteins?

Creation of amyloid fibrils, leading to diseases like Alzheimer's and Parkinson's Signup and view all the answers

What is the function of chaperone proteins?

To aid in correct folding by providing the right environment Signup and view all the answers

What is the result of cytokine binding to JAK-STAT receptors?

Signal transduction from the membrane to the signal transducer protein Signup and view all the answers

What is the function of serine-threonine kinase receptors?

To transduce signals from the membrane to the signal transducer protein Signup and view all the answers

What is the role of protein kinases in signal transduction?

To phosphorylate signal transducer proteins Signup and view all the answers

What is the function of hormone proteins?

To coordinate an organism's activities Signup and view all the answers

What is the result of protein misfolding and aggregation?

Creation of amyloid fibrils, leading to diseases like Alzheimer's and Parkinson's Signup and view all the answers

Study Notes

Covalent Modification

Phosphorylation, glycosylation, methylation, and acetylation are the most common forms of covalent modification.
Glycosylation is a post-translational modification.
Phosphorylation occurs when a protein kinase transfers a phosphate from ATP to the hydroxyl group of a specific serine, threonine, or tyrosine amino acid on the target enzyme, causing a conformational change that makes certain enzymes more or less active.
Dephosphorylation occurs when a protein phosphatase removes the phosphate by hydrolysis, reversing the effect of phosphorylation.
Phosphorylation adds two negative charges and can make H-bonds.

Zymogens and Proteolytic Cleavage

Zymogens are inactive enzymes that become active through proteolytic cleavage.
Proteolytic cleavage is an irreversible process that activates enzymes.
This process helps prevent enzymes from prematurely breaking down other proteins during their production or release.

Enzymes

Enzymes are catalysts that speed up the rate of reaction by lowering activation energy.
Enzymes regulate the rate of metabolic pathways in the body.
Allosteric regulation involves conformational changes that affect the catalytic site, and is achieved through allosteric activators or inhibitors binding to the active catalytic site.

Allosteric Regulation

Allosteric regulation can occur in two states: T (tense) with low affinity and R (relaxed) with high affinity.
Adenosine diphosphate (ADP) or adenosine monophosphate (AMP) are allosteric activators of PFK1, which is activated when ATP concentration in a muscle cell decreases.
ATP build-up inhibits PFK1.

Enzyme Regulation

Enzyme activity can be regulated by covalent modification, such as phosphorylation of an amino acid from the kinase domain.
Signal transduction occurs from the membrane to the signal transducer protein through covalent modification.

JAK-STAT Receptors

JAK-STAT receptors are heterodimers, consisting of two different proteins that bind together.
They are activated when a cytokine attaches, and JAK kinases bind to the heterodimers and phosphorylate each protein.
Signal transduction occurs from the membrane to the signal transducer protein.

Serine-Threonine Kinase Receptors

Cytokine dimer binds to heterodimers, and one heterodimer protein phosphorylates another, which then phosphorylates a signal transducer protein.

Protein Functions

Hormonal proteins coordinate an organism's activities, with examples including insulin.
Contractile and motor proteins facilitate movement, with examples including actin and myosin proteins.
Structural proteins provide structure and support, with three types of structural proteins.

Misfolding and Chaperone Proteins

Misfolded proteins can clump together, potentially harming cells.
Chaperone proteins aid in correct folding by providing the right environment for proper folding.
Misfolding can create amyloid fibrils, leading to diseases like Alzheimer's and Parkinson's.

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Description

This quiz covers the different types of covalent modifications, including phosphorylation, glycosylation, methylation, and acetylation. It also focuses on the role of protein kinases in phosphorylation.