How does the phosphorylation state of serine residues affect the catalytic activity of glycogen phosphorylase?

• A. Phosphorylated serine residues increase catalytic activity by favoring the r state.
• B. Phosphorylated serine residues decrease catalytic activity by favoring the t state.
• C. Phosphorylated serine residues decrease catalytic activity by favoring the r state.
• D. Phosphorylated serine residues have no effect on catalytic activity.

Answer: (A)