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kcat/Km in M⁻¹s⁻¹ from direct kcat or from Vmax/[E], with scientific-notation output and bands up to the diffusion-controlled perfection limit. Educational use only.
Execution
Fill in the form, run the tool, and review the result in one place.
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Tool usage guide
The Catalytic Efficiency Calculator determines kcat/Km in M⁻¹s⁻¹ for enzyme kinetics. Enter kcat and Km directly, or calculate kcat from Vmax and enzyme concentration before dividing by Km. Results use scientific notation and include an efficiency interpretation up to the diffusion-controlled limit.
Background
A hydrolase has a turnover number of 1000 s⁻¹ and a Km of 100 µM.
Problem
Calculate the enzyme's catalytic efficiency in M⁻¹s⁻¹.
How to use
Select Direct kcat + Km, enter kcat as 1000 per second, enter Km as 100 µM, and choose the required decimal places.
mode: direct; kcat: 1000 s⁻¹; Km: 100 µMOutcome
The calculator returns approximately 10⁷ M⁻¹s⁻¹ and labels the result very efficient.
Background
A saturated assay measures Vmax at 50 µM/min with 2 µM active enzyme sites. The enzyme's Km is 25 µM.
Problem
Obtain kcat from the assay data and calculate kcat/Km.
How to use
Select Vmax + [E] + Km, enter Vmax as 50 µM/min, enzyme concentration as 2 µM, and Km as 25 µM.
It measures catalytic efficiency and serves as a comparison metric for enzyme activity at low substrate concentration.
The result is reported in M⁻¹s⁻¹.
Yes. Select the Vmax + [E] + Km mode and enter Vmax in µM/min and enzyme concentration in µM.
Km can be entered in nanomolar, micromolar, or millimolar.
No. It is intended for educational use and laboratory planning.
mode: from-vmax; Vmax: 50 µM/min; enzyme concentration: 2 µM; Km: 25 µMOutcome
The calculator derives kcat as approximately 0.4167 s⁻¹ and returns kcat/Km of approximately 1.67 × 10⁴ M⁻¹s⁻¹, classified as modest.