Effect of ammonium, sodium, and potassium ions on rabbit muscle phosphofructokinase-1 and adenylate kinase activities.

Abstract

This report shows that 30 nM PFK-1 and 30 nM AK were both affected by the presence of NH(4)(+), Na(+), and K(+) salts but with opposite consequences. Low concentrations of PFK-1 lose about half of its activity as a result of dilution and become susceptible to further activity losses owing to the presence of monovalent salts. On the other hand low concentrations of AK lose about 75 percent of its activity but regains activity losses owing to the presence of monovalent salts. It was determined that regain of AK activity did not appear to be a reflection of a major effect on the K(m) value of either AMP or ATP. Dilution to 30 nM AK resulted in no increase K(m) values compared to K(m) values at 140 nM AK. Dilution caused major decreases in the maximum velocities, V(max), when ATP or fructose 6-phosphate was the variable substrate. It was shown in earlier reports that these same low concentrations of PFK-1 and AK were susceptible inhibitions by ascorbate. These attributes are discussed as they may relate to the role of ascorbate facilitation glycogen synthesis in resting muscle and the role that the cytoskeleton infrastructure scaffold may play is also discussed.