Enzyme Kinetics
Enzymes are biological catalysts capable of increasing the rate at which a chemical reaction occurs.
In single-substrate reactions, an enzyme @@E@@ catalyzes the conversion of a single substrate @@S@@ into a single product @@P@@ :
$$ \ce{E + S <=>[k_1][k_{-1}] ES ->[k_2] E + P} $$The reaction rate will be proportional to the concentration of the enzyme/substrate complex (@@ES@@) as given by:
$$ v = k_2[ES]$$At low concentrations of @@S@@ the concentration of @@ES@@ is directly proportional to @@[S]@@; therefore the velocity would depend on @@[S]@@ in an apparent first-order (linear) manner.
At very high concentrations of S, practically all the enzyme is in the form of the ES complex and the velocity depends on the rate of the conversion from ES to EP and the subsequent release of product and free enzyme. Adding more substrate would not effect a change in reaction velocity; so the slope of the plot of velocity versus @@[S]@@ approaches zero.
The rate equation that explains this behavior is known as the Michaelis—Menten equation:
$$ v = \frac{V_{max}[S]}{K_m + [S]}$$Where @@V_{max}@@ is the maximum reaction velocity (at an infinite substrate concentration):
$$ V_{max} = k_{cat}[E] = k_2[E]$$And where @@K_m@@ is known as the Michaelis-Menten constant and is defined as the substrate concentration at which the reaction velocity is half of the maximal velocity (@@V_{max}@@) obtained under saturating substrate conditions.
About this tool:
Use this tool to calculate the kinetic parameters from enzyme kinetic data.
This tool can calculate the Michaelis-Menten constant (@@K_m@@), the maximum rate (@@V_{max}@@) and the Hill coefficient (@@h@@) from reaction rate data as a function of substrate concentration.
Currently, only single-substrate kinetics are supported.
How to use this tool:
Input the reaction rate (@@v@@) as a function of substrate concentration [ @@S@@ ] in the table below. Only numbers are allowed!
You can type each value manually or paste the values from Excel or from another spreadsheet.
Select the units for the substrate concentration and for the rate using the dropdown lists. Note that:
1 Unit (U) = amount of the enzyme that catalyzes the conversion of 1 micromole of substrate per minute under the specified conditions of the assay
1 unit (u) = amount of the enzyme that catalyzes the conversion of 1 nanomole of substrate per minute under the specified conditions of the assay
You can add more rows or columns as needed.
Finally, select the type of model to use: Michaelis-Menten, Allosteric/Hill equation or both.
Click on "Submit" and get your results!