Regulation of phosphofructokinase by a new mechanism. An activation factor binding to phosphorylated enzyme.

Liver phosphofructokinase has been separated into three fractions by DEAE-cellulose chromatography.Chromatography of 32P-labeled enzyme reveals that the first fraction contains an average of 1.2 mol of phosphate/mol of enzyme (320,000 daltons), while the second and third fractions contain 3.3 mol of phosphate/ mol of enzyme.The high phosphate forms are much more sensitive to ATP inhibition than the low phosphate form.Recently, during the purification of liver phosphofructokinase, we found an activation factor which is bound to the enzyme and affects the activity (Furuya,