3. • Enzymes are the macromolecular biological catalysts. Enzymes accelerate or
catalyse the chemical reaction to yield the desired product. Like all catalysts,
enzymes increase the rate of reaction by lowering the activation energy and provide
an alternative path for the reaction to occur.
• Most enzymes are proteins, although few are catalytic RNA molecules. Enzymes
specifically comes from their unique three dimensional structure.
• Some enzymes can make their conversion of reactant to product occur many
millions of time faster. An extreme example is orotidine 5 phosphate decarboxylase ,
which allows a reaction that would otherwise takes million of year to occur in
millisecond.
• Chemically, enzymes are like any catalyst are not consumed in chemical reactions
(that’s mean they can be used again and again), nor they disturb the chemical
equilibrium condition of any chemical reaction.
• There is no any –ve type biocatalyst (enzyme).
4. The molecules upon which the enzymes act are called substrate and enzymes
converts theses molecules in to the different molecules (desired product).
Such as in fermentation process the sugar is converted into the alcohol
(ethanol) and carbon dioxide in the presence of yeast. So here the sugars
molecules are the substrates, and end products are the alcohol and carbon
dioxide, and yeast is as the enzyme.
Enzymes must bind their substrates before they can catalyse any chemical
reaction. Enzymes are usually very specific as to what substrate they bind
and then the chemical reaction catalysed. Specificity is with respect to the
complementary shape, charge and hydrophilic/hydrophobic characteristics
to the substrates.
5. The intermediate formed when a substrate molecule interacts with the active site of an
enzyme. When the enzyme is bonded to the substrate, we call this the enzyme
substrate complex. Once the reaction is complete, the enzyme releases and is ready
to bond with another substrate.
Following the formation of an enzyme–substrate complex, the substrate molecule
undergoes a chemical reaction and is converted into a new product.
Various mechanisms for the formation of enzyme–substrate complexes have been
suggested, including the induced-fit model and the lock-and-key mechanism.
6. An enzyme (E) molecule has a highly specific binding site or active site to which its substrate (S)
bind to produce enzyme-substrate complex (ES). The reaction proceeds at the binding site to
produce the products (P), which remain associated briefly with enzyme (enzyme-product
complex). The product is then liberated and the molecule is then freed in an active state to initiate
another round of catalysis. Apparently the affinity of binding site for the product is much lower than
that for the substrate.
Enzymes reduce the overall level of activation energy. Even a modest reduction in the value
of activation energy leads to very large increases in the reaction rates.
Most enzymatic reactions occur within a relatively narrow temperature range (usually from about
30°C to 40°C)
7. • The efficiency of an enzyme's activity is often measured by the turnover rate,
which measures the number of molecules of compound upon which the
enzyme works per molecule of enzyme per second. Carbonic anhydrase, which
removes carbon dioxide from the blood by binding it to water, has a turnover
rate of 106. That means that one molecule of the enzyme can cause a million
molecules of carbon dioxide to react in one second.
• Each enzyme has an optimal range of p H for activity; for example, pepsin in
the stomach has maximal reactivity under the extremely acid conditions of p H
1–3. Effective catalysis also depends crucially upon maintenance of the
molecule's elaborate three-dimensional structure. Loss of structural integrity,
which may result from such factors as changes in p H or high temperatures,
almost always leads to a loss of enzymatic activity. An enzyme that has been
so altered is said to be denatured.
8. In Food Processing,
the enzymes used include amylases from fungi and plants.
These enzymes are used in the production of sugars from starch, such as
in making high-fructose corn syrup. In baking, they catalyse the breakdown
of starch in the flour to sugar.
Yeast fermentation of sugar produces the carbon dioxide that raises the
dough.
Proteases are used by biscuit manufacturers to lower the protein level of
flour. Trypsin is used to predigest baby foods.
For the processing of fruit juices, celluloses and pectinases are used to
clarify fruit juices. Papain is used to tenderize meat for cooking.
9. In the brewing industry
Enzymess from barley are released during the mashing stage of beer production. They
degrade starch and proteins to produce simple sugar, amino acids, and peptides that are
used by yeast for fermentation.
In the paper industry
Amylases, xylanases, cellulases, and ligninases are used to degrade starch to lower
viscosity, aiding sizing and coating paper.
In the dairy industry,
Rennin, derived from the stomachs of young ruminant animals (like calves
and lambs) is used to manufacture of cheese, used to hydrolyze protein.
