Chemical Unfolding of Enolase from Saccharomyces cerevisiae Exhibits a Three-State Model

Enolase is a multifunctional protein that participates in glycolysis and gluconeogenesis and can act as a plasminogen receptor on the cell surface of several organisms, among other functions. Despite its participation in a variety of biological and pathophysiological processes, its stability and folding/unfolding reaction have not been fully explored. In this paper we present, the urea and GdnHCl-induced denaturation of enolase studied by means of fluorescence and circular dichroism spectroscopies. We found that enolase unfolds through a highly reversible pathway, populating a stable intermediate species in a range of experimental conditions. The refolding reaction also exhibits an intermediate state that might have a slightly more compact conformation compared to the unfolding intermediate. The thermodynamic parameters associated with the unfolding reaction are presented and discussed.