Chapter 13 Is glycolytic rate controlled by the reversible binding of enzymes to subcellular structures?

Publisher Summary This chapter analyzes the mechanism of glycolytic rate and glycolytic control. In the classical view, glycolytic flux is controlled primarily through allosteric regulation of four enzymes: glycogen phosphorylase (GP), hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK). Glycogen phosphorylase, HK, and PFK are found at the start of the glycolytic sequence, whereas PK is one of the terminal glycolytic enzymes. In fish, all four enzymes show several features common to many regulatory enzymes: they catalyze high energy steps that are (essentially) irreversible, they catalyze reactions that involve a high energy intermediate, and they are multi-subunit enzymes. They are also allosterically regulated by several different compounds, which serve to link enzyme activity to the energy state of the cell. The complexity of controls governing glycolytic enzyme activity becomes apparent when the widely different metabolic states that fish can endure are considered. The chapter examines the evidence for and against the formation of a functional glycolytic complex. It defines the glycolytic complex as a multi-enzyme structure containing all the enzymes necessary to metabolize glucose to pyruvate.