Day 35

Question 1

Glycogen Phosphorylase

Answer 1

Debranches glycogen to produce G1P that gets turned into G6P by phosphoglucomutase. Want active in “starved” state.
Allosteric Regulation
1) Activated by AMP
2) Inactivated by ATP and G6P
Covalent Modification
1) Phosphorylase Kinase directly adds phosphate
2)Protein Kinase A (PKA) adds phosphate to phosphorylase kinase to activate
3) Phosphoprotein phosphatase 1 dephosphorylates #1 and #2 and inactivates them

Question 2

Protein Kinase A (PKA)

Answer 2

• inactive tetramer with 2 regulatory and 2 catalytic subunits
• adenylate cyclase produces cAMP which binds to PKA’s regulatory units
• regulatory units bind to the catalytic unit’s kinase active site (autoinhibitor)

Question 3

Phosphorylase Kinase

Answer 3

• alpha, beta, sigma, gamma sub-units
• gamma is catalytic and others are regulatory
• max activation needs Ca2+ bound to the sigma unit (aka calmodulin) and phosphorylation on alpha and beta
• C-terminus tail is autoinhibitory but when PKA phosphorylates alpha and beta its okay

Question 4

Phosphoprotien Phosphatase-1

Answer 4

• inactivates phosphoylase kinase and glycogen phosphorylase by taking their phosphates.
• in a “less” active state, has glycogen,Gm subunit, and PP1c together.
• Site 1 of gets phosphorylated and becomes more active (insulin makes protein kinase which pushes this)
• Site 2 gets phosphorylated by epinephrine producing PKA. The two phosphates kick off PP1c and it is inactivated.

Question 5

Glycogenesis

Answer 5

producing glycogen

Question 6

Glycogenolysis

Answer 6

breaking down glycogen