The heat released during catalytic turnover enhances the diffusion of an enzyme

It has been traditionally assumed that the heat released during a single enzymatic catalytic event does not perturb the enzyme in any way; however, here single-molecule fluorescence correlation spectroscopy is used to show that, for enzymes that catalyse chemical reactions with large reaction enthalpies, the heat released at the protein's active site during catalysis transiently displaces the protein's centre-of-mass, essentially giving rise to a recoil effect that propels the enzyme. Enzymes can take the heat Enzymes catalyse chemical transformations by lowering the activation energy of those reactions. It is traditionally assumed that the heat released during a single catalytic event (a 'turnover' event) does not perturb the enzyme in any way. In this manuscript, the authors used single-molecule fluorescence correlation spectroscopy to show that for enzymes that catalyse chemical reactions with large reaction enthalpies (for example, catalase or alkaline phosphatase), the heat released at the protein's active site during catalysis transiently displaces the protein's centre-of-mass, essentially giving rise to a recoil effect that propels the enzyme. This work helps explain the recent finding that the diffusivity of enzymes increases in a substrate-dependent manner during catalysis. Recent studies have shown that the diffusivity of enzymes increases in a substrate-dependent manner during catalysis 1 , 2 . Although this observation has been reported and characterized for several different systems 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , the precise origin of this phenomenon is unknown. Calorimetric methods are often used to determine enthalpies from enzyme-catalysed reactions and can therefore provide important insight into their reaction mechanisms 11 , 12 . The ensemble averages involved in traditional bulk calorimetry cannot probe the transient effects that the energy exchanged in a reaction may have on the catalyst. Here we obtain single-molecule fluorescence correlation spectroscopy data and analyse them within the framework of a stochastic theory to demonstrate a mechanistic link between the enhanced diffusion of a single enzyme molecule and the heat released in the reaction. We propose that the heat released during catalysis generates an asymmetric pressure wave that results in a differential stress at the protein–solvent interface that transiently displaces the centre-of-mass of the enzyme (chemoacoustic effect). This novel perspective on how enzymes respon