How do you elucidate enzyme catalytic mechanisms?

Mechanism elucidation uses multiple complementary approaches. Kinetic analysis: steady-state kinetics reveals rate-limiting steps; pre-steady-state kinetics (stopped-flow, rapid quench) detects intermediates; isotope effects (kinetic isotope effects, positional isotope exchange) identify bond-breaking steps. Structural analysis: X-ray crystallography of substrate/product/inhibitor complexes, cryo-EM for dynamic states, and NMR for solution behavior. Chemical modification: active site labeling with mechanism-based inhibitors, site-directed mutagenesis of proposed catalytic residues. Computational: QM/MM simulations of reaction coordinates, molecular dynamics for conformational sampling. Model reactions: studying chemical analogs to test proposed chemistry. Integration of data constructs a consistent mechanism explaining all observations and testable predictions.