This page contains a RasMol (Chime) image of the protein phosphofructokinase (PFK), and the corresponding sequences of PFK for five genome organisms. These sequences were obtained by searching Genbank.

PFK is the allosteric enzyme that catalyzes the third step in glycolysis: the phosphorylation of fructose 6-phosphate to fructose 1,6-bisphosphate at the expense of one ATP.

Fig 1. The enzymatic mechanism of PFK. Courtesy of <http://biotech.icmb.utexas.edu>

PFK is the most important site of control in the glycolytic pathway of mammals. This is not surprising because PFK is the committed step of glycolysis. That is, it catalyzes the first irreversible reaction unique to the process. Its regulation is extremely significant considering that glycolysis has a dual role; not only does it degrade glucose to yield ATP, it provides the building blocks for synthetic reactions (such as fatty acid syntheses) as well. PFK is inhibited by ATP (signaling that cell energy stores are sufficient), low pH (to prevent excess fermentation products from being prduced), and citrate (which indicates that carbon skeletons are abundant). The enzyme is activated by ADP/AMP (which signals that the cell's energy stores are low), and fructose 2,6-bisphosphate.

Chime image (.pdb) of PFK

To view this graphic, you need the Rasmol plug-in

PFK Sequences in various genome organisms:

Reference:
Stryer, L. Biochemistry, fourth ed. W.H. Freeman and Co., New York: 1995.

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