Pig heart fumarase really does exhibit negative kinetic co-operativity at a constant ionic strength

Area of Science:

• Biochemistry
• Enzyme kinetics

Background:

• Fumarase is a key enzyme in the citric acid cycle.
• Previous studies suggested fumarase follows simple Michaelis-Menten kinetics.

Purpose of the Study:

• To investigate the kinetics of fumarase action on L-malate and fumarate.
• To evaluate reports of simple Michaelis-Menten kinetics for fumarase.

Main Methods:

• Enzyme kinetics assays were performed.
• Lineweaver-Burk plots were utilized.
• Constant ionic strength, pH, and buffer concentration were maintained.

Main Results:

• Lineweaver-Burk plots showed pronounced downward curvature.
• This curvature is indicative of negative kinetic co-operativity.
• Fumarase kinetics deviate from simple Michaelis-Menten models under specific conditions.

Conclusions:

• Fumarase does not strictly follow simple Michaelis-Menten kinetics.
• Negative kinetic co-operativity characterizes fumarase activity under the tested conditions.