Dissociation and catalysis in yeast hexokinase A

Area of Science:

• Biochemistry
• Enzymology
• Protein dynamics

Background:

• Yeast hexokinase A is a crucial enzyme in glucose metabolism.
• Understanding its activity regulation is key to metabolic pathway studies.

Purpose of the Study:

• To investigate the concentration- and temperature-dependent activity of yeast hexokinase A.
• To elucidate the role of glucose in regulating hexokinase A activity.

Main Methods:

• Enzyme activity assays at varying protein concentrations, pH, and temperatures.
• Analysis of enzyme kinetics and progress curves.

Main Results:

• Hexokinase A exhibits concentration-dependent specific activity, with a monomer-dimer equilibrium.
• Catalytic activity is lost upon dilution or high temperature but recovered upon cooling.
• Glucose binding prevents dilution-induced activity loss by stabilizing both monomer and dimer forms.
• Non-linear progress curves suggest dissociation of active dimers within ternary complexes.

Conclusions:

• Yeast hexokinase A activity is regulated by a pH- and temperature-dependent monomer-dimer equilibrium.
• The dimer is the catalytically active form, and glucose binding stabilizes it.
• Enzyme dissociation within ternary complexes may explain non-linear reaction kinetics.