Special Biochemistry Seminar

Over billions of years, organisms and their enzymes have been evolving and adapting in response to selection pressures from their environments. In particular, the mechanisms that underly the adaptation of enzyme activities and stabilities to environmental temperature are fundamental to our understanding of molecular evolution and how enzymes work. Here, we investigate the molecular and evolutionary mechanisms of enzyme temperature adaption, combining deep mechanistic studies with comprehensive sequence analyses of thousands of enzymes. We show that temperature adaptation in the model enzyme ketosteroid isomerase (KSI) has evolved repeatedly from primarily one residue change with limited, local epistasis, and we establish the underlying physical mechanisms. We further identify residues associated with organismal growth temperature across 1005 diverse bacterial enzyme families and assess the residue properties, molecular interactions, and interaction networks that appear to underly their activity and stability adaptation to temperature. Nevertheless, deeper studies of enzyme function and evolution required new tools. Enzymes are highly interconnected, involving many residues that come together to control function. Traditional methods to dissect enzymes, while invaluable, have limited throughput and typically just a handful of enzyme variants and properties can be studied in detail. Here we further develop and apply an emerging microfluidic method that allows us to measure ground-truth biochemical constants for thousands of enzyme variants in a single experiment. We leverage microfluidics to dissect enzyme temperature adaptation across several billion years of evolution, mapping the sequence-function landscape of enzyme function populated by a model enzyme family, adenylate kinase.