Abstract：
:The existence of temperature optima in enzyme catalysis that occur before protein melting sets in can be described by different types of kinetic models. Such optima cause distinctly curved Arrhenius plots and have, for example, been observed in several cold-adapted enzymes from psychrophilic species. The two main explanations proposed for this behavior either invoke conformational equilibria with inactive substrate-bound states or postulate differences in heat capacity between the reactant and transition states. Herein, we analyze the implications of the different types of kinetic models in terms of apparent activation enthalpies, entropies, and heat capacities, using the catalytic reaction of a cold-adapted α-amylase as a prototypic example. We show that the behavior of these thermodynamic activation parameters is fundamentally different between equilibrium and heat capacity models, and in the α-amylase case, computer simulations have shown the former model to be correct. A few other enzyme-catalyzed reactions are also discussed in this context.
journal_name
Biochemistryjournal_title
Biochemistryauthors
Åqvist J,Sočan J,Purg Mdoi
10.1021/acs.biochem.0c00705subject
Has Abstractpub_date
2020-10-13 00:00:00pages
3844-3855issue
40eissn
0006-2960issn
1520-4995journal_volume
59pub_type
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