Enzyme catalysis

Abstract: The three-dimensional structure of proteins chemical catalysis the basic equations of enzyme kinetics measurement and magnitude of enzymatic rate constants the pH dependence of enzyme catalysis practical kinetics detection of intermediaries in reactions by kinetics stereochemistry of enzymic reactions active-site-directed and enzyme-activated irreversible inhibitors - affinity labels and suicide inhibitors conformational change, allosteric regulation, motors and work forces between molecules, and enzyme-substrate binding energies enzyme-substrate complementarity and the use of binding energy in catalysis specificity and editing mechanisms recombinant DNA technology case studies of enzyme structure and mechanism protein engineering protein stability kinetics of protein folding folding pathways and energy landscapes.

Abstract: A Brief History of Enzymology. Chemical Bonds and Reactions in Biochemistry. Structural Components of Enzymes. Protein-Ligand Binding Equilibria. Kinetics of Single-Substrate Enzyme Reactions. Chemical Mechanisms in Enzyme Catalysis. Experimental Measures of Enzyme Activity. Reversible Inhibitors. Tight Binding Inhibitors. Time-Dependent Inhibition. Enzyme Reactions with Multiple Substrates. Cooperativity in Enzyme Catalysis. Appendices. Index.

Abstract: A unique feature of chemical catalysis mediated by enzymes is that the catalytically reactive atoms are embedded within a folded protein. Although current understanding of enzyme function has been focused on the chemical reactions and static three-dimensional structures, the dynamic nature of proteins has been proposed to have a function in catalysis. The concept of conformational substates has been described; however, the challenge is to unravel the intimate linkage between protein flexibility and enzymatic function. Here we show that the intrinsic plasticity of the protein is a key characteristic of catalysis. The dynamics of the prolyl cis-trans isomerase cyclophilin A (CypA) in its substrate-free state and during catalysis were characterized with NMR relaxation experiments. The characteristic enzyme motions detected during catalysis are already present in the free enzyme with frequencies corresponding to the catalytic turnover rates. This correlation suggests that the protein motions necessary for catalysis are an intrinsic property of the enzyme and may even limit the overall turnover rate. Motion is localized not only to the active site but also to a wider dynamic network. Whereas coupled networks in proteins have been proposed previously, we experimentally measured the collective nature of motions with the use of mutant forms of CypA. We propose that the pre-existence of collective dynamics in enzymes before catalysis is a common feature of biocatalysts and that proteins have evolved under synergistic pressure between structure and dynamics.

Abstract: The seminal hypotheses proposed over the years for enzymatic catalysis are scrutinized. The historical record is explored from both biochemical and theoretical perspectives. Particular attention is given to the impact of molecular motions within the protein on the enzyme's catalytic properties. A case study for the enzyme dihydrofolate reductase provides evidence for coupled networks of predominantly conserved residues that influence the protein structure and motion. Such coupled networks have important implications for the origin and evolution of enzymes, as well as for protein engineering.