1. Enzymes are protein catalysts that increase the rate of biochemical reactions without being consumed. They have high molecular weights and are made up of amino acid chains. 2. Most enzymes consist of both a protein portion (apoenzyme) and a non-protein component (cofactor). Together, these form the functional holoenzyme. 3. Extracellular enzymes are often involved in breaking down large molecules outside cells. They allow nutrients to pass through cell membranes and are important in digestion and microbial processes like virulence and bioremediation.

2. Topic name: What is enzyme and characteristics of extracellular enzymes
Assigned by Sir Dr Abdul Nabi Merjat
Subject: Enzyme technology
Name: Allah bux baloch 2k14 MB 63

3. Contents:
Introduction
Chemical nature of enzyme
Structure of enzyme
Enzyme Components
Entracellular and extracellular enzymes
Characteristics of extra cellular enzyme
References

4. Enzymes
Enzymes are biocatalysts, the catalysts of life.
A catalysts is defined as a substance that increase the velocity or rate of chemical
reaction without itself undergoing any change in the overall process

5. Chemical Nature of Enzymes
All known enzymes are proteins. They are high molecular weight compounds made
up principally of chains of amino acids linked together by peptide bonds.
Enzymes can be denatured and precipitated with salts, solvents and other reagents.
They have molecular weights ranging from 10,000 to 2,000,000.

8. Enzyme Components
Although some enzymes consist entirely of proteins, most consist of both a protein
portion, called an apoenzyme. and a nonprotein component, called a cofactor. Ions of
iron, zinc, magnesium, or calcium are examples of cofactors. If the cofactor is an
organic molecule, it is called a coenzyme.
Apoenzymes are inactive by themselves; they must be activated by cofactors.
Together, the apoenzyme and cofactor form a holoenzyme. or whole, active enzyme.
If the cofactor is removed, the apoenzyme will not function.
Or
The functional unit of the enzyme is known as holoenzyme which is often made up of
apoenzyme (the protein part ) and coenzyme( non protein organic part).

10. Characteristics of exoenzymes
Most often these enzymes are involved in the breakdown of larger macromolecules.
The breakdown of these larger macromolecules is critical for allowing their
constituents to pass through the cell membrane and enter into the cell.
For humans and other complex organisms, this process is best characterized by
the digestive system which breaks down solid food via exoenzymes.
The small molecules, generated by the exoenzyme activity, enter into cells and are
utilized for various cellular functions.

11. Bacteria and fungi also produce exoenzymes to digestnutrients in their environment,
and these organisms can be used to conduct laboratory assays to identify the
presence and function of such exoenzymes.
Some pathogenic species also use exoenzymes as virulence factors to assist in the
spread of these disease causing microorganisms.
In addition to the integral roles in biological systems, different classes
of microbial exoenzymes have been used by humans since pre-historic times for such
diverse purposes as food production, biofuels, textile production and in the paper
industry.
Another important role that microbial exoenzymes serve is in the natural ecology
and bioremediation of terrestrial and marine environments.

12. Examples of exoenzymes as virulence factors
Necrotizing enzymes
Necrotizing enzymes destroy cells and tissue.
coagulase
By binding to prothrombin, coagulase facilitates clotting in a cell by ultimately
converting fibrinogen to fibrin.

13. Kinases
The opposite of coagulase, kinases can dissolve clots. S. aureus can also produce
staphylokinase, allowing them to dissolve the clots they form, to rapidly diffuse into
the host at the correct time.
Hemolysins
Hemolysins target erythrocytes, or red blood cells. Attacking and lysing these cells
allows the pathogen to harm the host organism, and also provides it with a source
iron from the lysed hemoglobin, like the fungus Candida albicans.

14. Examples of digestive exoenzymes
Amylases
Amylases are a group of extracellular enzymes (glycoside hydrolases) that catalyze
the hydrolysis of starch into maltose.
Lipoprotein lipase
Lipoprotein lipase (LPL) is a type of digestive enzyme that helps regulate the uptake
of triacylglycerols from chylomicrons and other low-density lipoproteins from fatty
tissues in the body
Pectinase
Pectinases, also called pectolytic enzymes, are a class of exoenzymes that are involved
in the breakdown of pectic substances.
Pepsin
Pepsin works to break down proteins in foods such as dairy, meat, and eggs.
Trypsin
This enzyme is responsible for the breakdown of large globular proteins.

15. Amylase
Amylase breaks down carbohydrates into mono- and disaccharides, so
must be used for this assay. Once the bacteria is streaked on the agar, the plate is
flooded with iodine. Since iodine binds to starch but not its digested byproducts, a
clear area will appear where the amylase reaction has occurred. Bacillus subtilis is a
bacterium that results in a positive assay as shown in the picture

16. References
Biochemistry U Satyanarayana
Microbiology 10th edition by Tortora
And
Wikipedia . 13/04/2017 . 03:05Am