The mechanism by which enzymes catalyse chemical reactions begins with the binding of the substrates to the active site on the enzyme.
Enzymes are biological catalysts. Catalysts are substances that increase the rate of chemical reactions without being used up. Enzymes are also proteins that are folded into complex shapes that allow smaller molecules to fit into them. The place where these substrate molecules fit is called the active site.Examples are lactase, alcohol dehydrogenase and DNA polymerase.
Characterisitcs of enzyme
Enzymes possess great catalytic power.
Enzymes are highly specific.
Enzymes show varying degree of specificities.
Absolute specificity where the enzymes react specifically with only one substrate.
Stereo specificity is where the enzymes can detect the different optical isomers and react to only one type of isomer.
Reaction specific enzymes, these enzymes as the name suggests reacts to specific reactions only.
Specificity and efficiency of enzymes
Specificity: Each enzyme catalyses only one chemical reaction. Efficiency: They are very efficient catalysts. They speed up the rate of reaction by factors of upto 1020
High efficeieny of a small quantity of enzymes
The reason is that enzymes are also generated after their catalytic activity but their rate of regeneration is very fast, of the order of 1 million times per minute.
Optimum temperature and pH of enzyme
Enzyme catalysed reactions have maximum rate at physiological pH of around 7.4 and human body temperature of 37oC under one atm pressure.
Mechanism of enzyme catalysis
mechanism of enzyme catalysis proceed in two steps: Step 1: Binding of substrate to enzyme to form activated complex. E+S→ES Step 2: Decompostion of the activated complex to form product. ES→E+P
Intermediate compound formation theory
According to this theory, the desired reaction is brought about by a path involving the formation of an unstable intermediate compound, followed by its decomposition into the desired end products with the regeneration of the catalyst. (a) When the intermediate compound is reactive and reacts with the other reactants.
On a molecular level, most catalysts (or most substances really) are not just flat surfaces, they have complex three-dimensional shapes. The substrate often has to bind to the catalyst in a very specific way in order for the catalysed reaction to take place - this is the active centre.