Membrane enzymes: artifacts in Arrhenius plots due to temperature dependence of substrate-binding affinity.

For the membrane sodium-stimulated magnesium-adenosinetriphosphatase of Acholeplasma laidlawii B both the Vmax and Km values in the Michaelis equation very strongly with temperature. Simulations of Arrhenius plots show that an enzyme with a temperature-dependent Km can yield a variety of Arrhenius plot artifacts, most notably erroneous "breaks," if activity is assayed at a fixed substrate concentration.