Chapter 2 ( Dr. Ali Coşkun DALGIÇ )

FE 462 BIOCHEMICAL ENGINEERING
Enzyme Kinetics
INTRODUCTION
Enzymes are biological catalysts that are protein molecules in nature.
They are produced by living cells (animal, plant, and microorganism) and are absolutely essential as catalysts in biochemical reactions.
INTRODUCTION
Enzyme reactions are different from chemical reactions, as follows:
1. An enzyme catalyst is highly specific, and catalyzes only one or a small number of chemical reactions. A great variety of enzymes exist, which can catalyze a very wide range of reactions.
2. The rate of an enzyme-catalyzed reaction is usually much faster than that of the same reaction when directed by non-biological catalysts. Only a small amount of enzyme is required to produce a desired effect.
3. The reaction conditions (temperature, pressure, pH, and so on) for the enzyme reactions are very mild.
4. Enzymes are comparatively
Nomenclature of Enzymes
Commercial Applications of Enzymes
1. Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases
ENZYME KINETICS
Assume that a substrate (S) is converted to a product (P) with the help of an enzyme (E) in a reactor as
The effect of substrate concentration on the initial reaction rate
From these curves we can conclude the following:
1. The reaction rate is proportional to the substrate concentration (that is, first-order reaction) when the substrate concentration is in the low range.
2. The reaction rate does not depend on the substrate concentration when the substrate concentration is high, since the reaction rate changes gradually from first order to zero order as the substrate concentration is increased.
3. The maximum reaction rate rmax is proportional to the enzyme concentration within the range of the enzyme tested.
ENZYME KINETICS
The mechanism of one substrate-enzyme reaction can be expressed as
Michaelis-Menten Approach
If the slower reaction, determines the overall rate of reaction, the rate of product formation and substrate consumption is proportional to the concentration of the enzyme-substrate complex as:
EVALUATION OF KINETIC PARAMETERS
The Michaelis-Menten equation can be rearranged to be expressed in linear form. This can be achieved in three ways:
INHIBITION OF ENZYME REACTIONS
A modulator (or effector) is a substance which can combine with enzymes to alter their catalytic activities. An inhibitor is a modulator which decreases enzyme activity. It can decrease the rate of reaction either competitively, noncompetitively, or partially competitively
OTHER INFLUENCES ON ENZYME ACTIVITY
The rate of an enzyme reaction is influenced by various chemical and physical conditions. Some of the important factors are the concentration of various components (substrate, product, enzyme, cofactor, and so on), pH, temperature, and shear. The effect of the various concentrations has been discussed earlier.
OTHER INFLUENCES ON ENZYME ACTIVITY
Case Study
Case Study

Facebook Yorumları

Bir Cevap Yazın