OC3 - phosphorylation and dephosphorylation

Question 1

covalent modification

Answer 1

covalent bonds are made of broken
changes an enzymes shape, making the enzyme either active or inactive, so, the concentration of active enzyme is changed therefore the reaction rate is changed

Question 2

phosphorylation

Answer 2

an important regulatory mechanism
the addition of a phosphate (PO4) group to a protein molecule through a condensation reaction
enzymes called kinase and phosphatases are involved in phosphorylation
results in a conformational change in the proteins structure causing them to become activated or deactivated.
usually occurs on serine, threonine, and tyrosine residues due to the presence of a hydroxyl group making them polar - the phosphate gets added to the polar end of the R-group of the amino acid through a condensation reaction.

Question 3

protein kinases

Answer 3

involved in phosphorylation (add phosphate group)
the addition of a phosphate group adds an extra two negative charges to a modified protein: new electrostatic interaction can be formed resulting in altered substrate binding and catalytic activity.
vary in their degree of specificity.
dedicated > phosphorylate a single protein, or, several closely related ones
multifunctional > can modify many targets, and recognise related sequences
the primary determinant of specificity is the amino acid sequence surrounding the phosphorylation site.

Question 4

protein phosphatases

Answer 4

involved in dephosphorylation (remove phosphate group)
reverse the effects of kinases by catalysing the hydrolytic removal of phosphate groups attached to proteins.

Question 5

consensus sequence

Answer 5

the consensus sequence recognised by protein kinase A is :
arg-arg-X-ser-Z or
arg-arg-X-thr-Z