Properties of rat lens phosphofructokinase.
Two interconvertible forms of phosphofructokinase (PFK) have been eluted from a DEAE-cellulose column from the supernatant fraction of rat lens homogenates centrifuged at 96,000 x g for 1 hour at 0 to 4 degrees C. The interconversion can be manipulated by a change in the pH of the extracting and eluting buffers. PFK-I is the dominant form at pH between 7.4 to 7.05, while PFK-II dominates at pH 7.4 to 8.2. PFK-II is believed to be the functional form; it is inhibited by high concentrations of ATP and the inhibitory effect is enhanced by more acidic pH. Fructose-6-phosphate counteracts ATP inhibition, but the most potent de-inhibitors are ADP and AMP. Among the inorganic ions tested, sulfate, phosphate, ammonium, and potassium also de-inhibit, whereas calcium further inhibits the enzyme. The behavior of PFK under physiologic conditions and the significance of the presence of two forms of PFK in the lens are discussed.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D005636:Fructosephosphates / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007908:Lens, Crystalline / Q000201:enzymology*; D008099:Liver / Q000201:enzymology; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology; D010710:Phosphates / Q000494:pharmacology; D010732:Phosphofructokinase-1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology; D013431:Sulfates / Q000494:pharmacology
D005636:Fructosephosphates; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D013431:Sulfates; D012965:Sodium Chloride; D000255:Adenosine Triphosphate; D010732:Phosphofructokinase-1; D008274:Magnesium; D011188:Potassium; D002118:Calcium