In this model, the substrate is strained due to the induced conformation change in the enzyme. It is also possible that when a substrate binds to the preformed active site, the enzyme induces a strain to the substrate, which leads to the formation of product as given in Figure 6.18. The concept of substrate strain explains the…

Koshland (1958) proposed a more susceptible and realistic model for enzyme-substrate complex formation. As per this model, the active site is rigid or pre-shaped. The essential features of the substrate binding site are present at the nascent active site. The interaction of the substrate with the enzyme induces fit or a conformation change in enzyme, resulting…

This theory was proposed by a German biochemist Emil Fischer in 1898. This is, in fact, the very first model proposed to explain an enzyme-catalysed reaction. According to this model, the substrate or conformation of enzyme is rigid. The substrate fits to the binding site (active site) just as a key fits to the proper…

The prime requisite for enzyme catalysis is that the substrate [S] must combine with the enzymes [E] at the active site to form an enzyme. Substrate complex [ES] ultimately results in the product formation.   E + S  ES  E + P A few theories have been put forth to explain the mechanism of enzyme substrate complex…

This (Eadie–Hofstee) transformation is used to avoid the bunching of values that—at the lower end of double reciprocal plot as shown in Figure 6.14. Multiplied Vo Vmax Figure 6.14 Eadie–Hofstee Plot

When [S] is lesser than Km, the velocity of the reaction is roughly proportional to the substrate concentration. The rate of the reaction is said to be first order with respect to substrate. When [S] is greater than Km, the velocity of the reaction is constant and is equal to Vmax. Now the rate of…

A numerically high Km reflects a low affinity for substrate (e.g. hexokinase) as shown in Figure 6.12. Because a high concentration of substrate is needed to half the substrate of the enzyme. Figure 6.12 Graphical Representation of Km for Different Enzymes with Substrate Affinity

A numerically small (low) Km reflects a high affinity of enzyme for substrate (e.g. glucokinare) as shown in Figure 6.12. Because low concentration of substrate is needed to half the substrate of the enzyme, that is, to reach a velocity that is ½Vmax.

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