Mammalian aldolases are isomer-selective high-affinity inositol polyphosphate binders

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Inositol polyphosphates are crucial signaling molecules in mammalian cells.
• Fructose 1,6-bisphosphate aldolases (ALDOA and ALDOB) are key glycolytic enzymes.
• The interaction between aldolases and inositol polyphosphates has not been extensively characterized.

Purpose of the Study:

• To identify target proteins of inositol polyphosphates in mammalian tissues.
• To investigate the binding characteristics and inhibitory effects of inositol polyphosphates on fructose 1,6-bisphosphate aldolases.

Main Methods:

• Protein binding assays using tryptophan fluorescence quenching and difference spectroscopy.
• Equilibrium dialysis for aldolase A binding studies.
• Enzyme activity assays to determine inhibition kinetics.

Main Results:

• Fructose 1,6-bisphosphate aldolases (ALDOA and ALDOB) are identified as potent, isomer-selective binders of inositol polyphosphates.
• Inositol 1,4,5-trisphosphate exhibited the strongest binding affinity for both aldolase A and aldolase B.
• Binding of inositol polyphosphates induced conformational changes and inhibited enzyme activity in a competitive or complex cooperative manner.

Conclusions:

• Aldolases possess a significant capacity to bind inositol 1,4,5-trisphosphate, even in the presence of excess substrate.
• The observed binding and inhibition suggest a regulatory role for aldolase-inositol polyphosphate interactions.
• Further research is warranted to elucidate the physiological implications of these interactions in cellular metabolism and signaling.