ACCU-RATES: A Web Tool for Accurate Enzyme Kinetics and Initial Reaction Rate Measurements

Accurate determination of initial reaction rates (v₀) is essential for characterizing enzyme function, designing inhibitors, and modeling biological systems. Traditional methods rely on linear approximations valid for reaction phases difficult to capture, while substrate excess over the enzyme does not ensure constant rates. To overcome these limitations, we developed ACCU-RATES, a user-friendly web tool that analyzes heuristically product accumulation or substrate depletion curves containing at least two time points. Using a differential form of the Michaelis-Menten equation, ACCU-RATES numerically fits progress curves to interpolate v₀, enabling precise determination of the Michaelis constant (K_m) and limiting rate (V). Simulations across diverse scenarios, including data noise and low sampling rates, show that ACCU-RATES delivers reliable, user-independent parameter estimates without relying on linear phases. Compared to existing methods, it offers superior accuracy and robustness against assay interferences, with applications in inhibitor discovery, synthetic biology, and biomarker assays. ACCU-RATES is freely available at https://accu-rates.i3s.up.pt.