The combined effects of reactant kinetics and enzyme stability explain the temperature dependence of metabolic rates

Authors

John DeLong, University of Nebraska – LincolnFollow
J. P. Gibert, University of Nebraska – Lincoln
Thomas M. Luhring, University of Nebraska-LincolnFollow
Gwendolyn C. Bachman, University of Nebraska-LincolnFollow
B. Reed, University of Nebraska – Lincoln
A. Neyer, University of Nebraska – Lincoln
Kristi Montooth, University of Nebraska – LincolnFollow

ORCID IDs

John DeLong http://orcid.org/0000-0003-0558-8213

Date of this Version

3-7-2017

Citation

www.ecolevol.org Ecology and Evolution. 2017;7:3940–3950.

Comments

2017 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License

Abstract

A mechanistic understanding of the response of metabolic rate to temperature is essential for understanding thermal ecology and metabolic adaptation. Although the Arrhenius equation has been used to describe the effects of temperature on reaction rates and metabolic traits, it does not adequately describe two aspects of the thermal performance curve (TPC) for metabolic rate—that metabolic rate is a unimodal function of temperature often with maximal values in the biologically relevant temperature range and that activation energies are temperature dependent. We show that the temperature dependence of metabolic rate in ectotherms is well described by an enzyme-assisted Arrhenius (EAAR) model that accounts for the temperature-dependent contribution of enzymes to decreasing the activation energy required for reactions to occur. The model is mechanistically derived using the thermodynamic rules that govern protein stability. We contrast our model with other unimodal functions that also can be used to describe the temperature dependence of metabolic rate to show how the EAAR model provides an important advance over previous work. We fit the EAAR model to metabolic rate data for a variety of taxa to demonstrate the model’s utility in describing metabolic rate TPCs while revealing significant differences in thermodynamic properties across species and acclimation temperatures. Our model advances our ability to understand the metabolic and ecological consequences of increases in the mean and variance of temperature associated with global climate change. In addition, the model suggests avenues by which organisms can acclimate and adapt to changing thermal environments. Furthermore, the parameters in the EAAR model generate links between organismal level performance and underlying molecular processes that can be tested for in future work.