Rate of formation of [ES] complex Let ET be the total concentration of enzyme both free [E] and bound [ES], and then the concentration of free enzyme [E] will be   [E] = [ET] – [ES] Let [S] be the concentration of substrate in free form; then the rate of formation of [ES] is given…

According to Michaelis and Menten, the rate determining the step (slowest) of the reaction is the breakdown of the enzyme substrate complex [ES]. Thus, the velocity V of the overall reaction, according to the law of mass action, is given by

Michaelis–Menten (M–M) theory is based on two important assumptions:

It was Michaelis and Menten, in 1913, who proposed a successful explanation for the effect of substrate concentration on the enzyme activity. According to them, enzyme (E) and substrate (S) combine rapidly to form a complex, the enzyme substrate complex (ES) or Michaelis constant. This complex then breaks down relatively slowly to form the product (P)…

INTRODUCTION Enzyme kinetics is the most powerful technique for elucidating the catalytic mechanisms of enzymes. Almost all the enzyme-catalysed reactions involve more than one substrate. Although the single-substrate enzyme reaction is something of a ‘rarity’ in biochemical systems, it nevertheless represents a very useful simple model for the development and discussion of theories of enzyme…

As the substrate molecules are comparatively much smaller than the enzyme molecules, there should be some specific regions or sites on the enzyme for binding with substrate. Such sites of attachment are variously called active sites or catalytic sites or substrate sites. Active site of an enzyme as shown in Figure 6.6. Figure 6.6 Diagrammatic Representation of Active Site…

The pH value or the hydrogen ion concentration of the medium (buffers) controls the activity of an enzyme to a great extent. This is mainly related to the degree of dissociation, the electric charge of enzyme, and through this, the formation of enzyme substrate complex. Each enzyme acts best in a certain pH, which is…

The rate of an enzyme action increase with the rise in temperature of 10°C is called temperature quotient or Q10 (which means enzyme activity is increased two to three times for a rise in temperature of 10°C). The optimum temperature for most of the enzymes varies from 30°C–40°C. Example: Catalase optimum temperature is 30°C. The enhanced…

The reactants or substrates require energy before they start to react. For this reaction, it takes time if enzymes are not present, but in the presence of enzyme, it reduces the activation or transition energy and favours the reaction as shown in Figure 6.3. Figure 6.3 Effect of Enzyme on Activation Energy of a Reaction (A is…

An enzyme is a catalyst, and it cannot alter the equilibrium of a chemical reaction. This means that an enzyme accelerates the forward and reverse reaction by some factors precisely. To attain this equilibrium without enzymes, it takes several hours, but with enzymes, it is attained within a second. Thus, enzymes accelerate the attachment of…