Enzyme kinetics

Enzyme kinetics is the study of the chemical reactions that are catalyzed by enzymes. In enzyme kinetics, the reaction rate is measured and the effects of varying the conditions of the reaction are investigated. Studying an enzyme's kinetics in this way can reveal the catalytic mechanism of this enzyme, its role in metabolism, how its activity is controlled, and how a drug or an agonist might inhibit the enzyme.

Introduction

Enzymes are molecules that manipulate other molecules — the enzymes' substrates. These target molecules bind to an enzyme's active site and are transformed into products through a series of steps known as the enzymatic catalytic cycle. Enzymes can catalyze up to several million reactions per second. Enzyme rates depend on solution conditions and substrate concentration.

Enzyme Kinetic Models

Michaelis-Menten Kinetics

The Michaelis-Menten model is the one of the simplest and best-known approaches to enzyme kinetics. It takes the name from Leonor Michaelis and Maud Menten. This kinetic model is valid when the assumption of steady state can be made, which is that the concentration of the enzyme-substrate complex (ES) is constant over time.

Briggs-Haldane Kinetics

The Briggs-Haldane model is derived from the quasi-steady-state approximation (QSSA). The QSSA assumes that a quasi-steady state is formed in which the rate of formation of ES is equal to the rate of its consumption.

Hill Kinetics

Hill kinetics is used when the substrate can bind more than one enzyme at a time. It is a special case of the general equations given above. It was first introduced by Archibald Hill.

Factors Affecting Enzyme Activity

Enzyme activity can be affected by a variety of factors, such as temperature, pH, and concentration. Enzymes work best within specific temperature and pH ranges, and sub-optimal conditions can cause an enzyme to lose its ability to bind to a substrate.

Inhibition

Enzyme inhibitors are molecules that bind to enzymes and decrease their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors.

See Also

• Enzyme inhibitor
• Enzyme catalysis
• Enzyme assay
• Enzyme activator