velocity for an enzyme-catalyzed reaction =
= ((maximum velocity) * (substrate concentration)) / ((Km) + (substrate concentration))
where:
• The maximum velocity (Vmax) is the plateau reaction velocity reached as the substrate concentration increases.
• Km is the substrate concentration at which the velocity for the reaction is half of the maximum velocity.
This can be rearranged to give the substrate concentration for a given velocity:
substrate concentration =
= ((velocity) * (Km)) / ((maximum velocity) - (velocity))
Expressing the activity of an enzyme:
• A common measure for enzyme activity is the "unit"of enzyme activity, which is the amount of enzyme which catalyzes the conversion of 1 µmol of substrate per minute under a defined environment of temperature, pH and other factors.
• The katal is a unit recommended by the International Union of Biochemistry and is the amount of enzyme that will convert 1 mole of substrate per second under a defined environment.
• One unit of enzyme activity is equivalent to 16.67 nanokatal (nkat).
