Regulation of Canine Skeletal Muscle Phosphofructokinase-1 by Adenine Nucleotides

摘要

Phosphofructokinase-1 (PFK-1) is the most important rate-controlling enzyme for glycolysis in both prokaryotes and eukalyotes. PFK-1 activity is regulated by multiple cellular metabolites, including nucleotides. Intracellular nucleotides are produced through various metabolic processes, including energy metabolism and intracellular signaling pathways. The activity of PFK-1, purified from canine skeletal muscle, was evaluated in the presence of various concentrations of adenine nucleotides to examine the regulation of glucose catabolism in canine skeletal muscle. Although UTP did not inhibit PFK-1 activity to the same extent as ATP, it substituted for ATP as a phosphate donor. cAMP functioned in a similar manner as AMP, as an activating effector of the PFK-1 reaction. ADP activated PFK-1 at low concentrations, but slightly inhibited PFK-1 at higher concentrations. The results suggested that canine PFK-1 had three different binding sites for adenine nucleotides acting as phosphate donors, activating effectors, and inhibitory effectors. Moreover, PFK-1 was shown to be activated by AMP and inhibited by ATP, while UTP and cAMP regulated PFK-1 activity. The results also suggested that ADP binds to the allosteric sites (for ATP and AMP) of PFK-1. Each adenine nucleotide functions as either an activating or inhibitory effector of PFK-1 reaction in canine skeletal muscle. Therefore, intracellular nucleotides may play an important role in regulating glucose metabolism by binding to the allosteric site of the enzyme.