Characteristics of Km The Michaelis–Menten constant is characteristics of an enzyme and a substrate and reflects the affinity of the enzyme for that substrate. Km is numerically equal to the substrate concentration, of which the reaction velocity is equal to ½Vmax. Km does not vary with the concentration of enzyme.
Transformation of M–M equation is given in Table 6.6. Table 6.6 Transformation of M–M Equation
According to M–M equation, at very high values of [S], the initial velocity Vo asymptotically approaches Vmax. In practice, however, it is very difficult to accurately assess Vmax from direct plots of Voversus[S] (from hyperbola curve). Only when the graph is linear, we can determine the Vmax. Therefore, the M–M equation is algebraically transformed into other forms…
M–M equation is sufficient to describe most of the enzyme-catalysed reaction. It can be utilised to determine Km and Vmax at various substrate concentration, and the values can be used in predicting rate-limiting steps
The Km value can be determined from Michaelis plot, LB plot, and Eadie Hofstee’s plot.
It is independent of enzyme concentration but dependent on substrate conc. It varies with pH and temperature. Typically, the Km values lie between 10−2 to 10−5 moles/litre for various enzymes as given in Table 6.4. Table 6.4 Km Value for Different Enzymes
Definition It is defined as the concentration of the substrate at which the initial rate is half the maximal rate.