Molecular and kinetic alterations of muscle AMP deaminase during chronic creatine depletion

Chronic creatine depletion through long-term feeding of the creatine analog beta-guanidinopropionic (beta-GPA) acid induces reduced AMP deaminase (AMPD) levels but does not affect peak AMPD activity levels in rat fast-twitch muscles. Kinetic analyses were carried out to determine the mechanism of this maintenance of enzyme activity. Results reveal that enzymes from beta-GPA-fed rats had an additional high-affinity Michaelis-Menten constant accounting for the enhanced activity given the low concentration of AMP.