1. Biochemistry (Lippincott's Illustrated Reviews Series), 6E
Enzymes
OMAR A. ALOMAIR
Biochemistry 1
References
Biochemistry (Lippincott's Illustrated Reviews Series), 6E

2. Enzymes Almost every reaction that happen in the body involves enzymes
They function as a catalyst from physiological reaction
Enzymes control in a selective manner reactants in chemical reactions
These reactants are called substrate
Consequently, Enzymes mediate all metabolic interactions in the body

3. Enzymes Nomenclature Enzymes are usually named in two ways
The first one is the “Recommended naming system”
This naming scheme is more appropriate and easier for every day use
The second is the “Systematic naming system”
This naming scheme is more complicated and is required to accurately describe an enzyme

4. Enzymes Nomenclature “Recommended naming system”
The commonly encountered enzymes are giving the suffix “ase”
The “ase” suffix is linked the substrate of the reaction, e.g. glucosidase and urease
Or it is attached to the characteristic of the chemical reaction, e.g. lactate dehydrogenase and adenylyl cyclase
However, a number of enzymes are usually named arbitrarily without a description of their functions, e.g. trypsin and pepsin

5. Enzymes Nomenclature “Systematic naming system”
According to this nomenclature, all enzymes are classified under 6 classes
For any enzyme, the suffix “ase” is part of the chemical modification initialed by the enzyme
Additionally, all the involved substrates written a head of the chemical reaction, e.g. lactate :NAD+ oxidoreductase
Although this naming scheme is very informative, it can be a bit confusing and unwieldy

6. Enzymes Nomenclature “Systematic naming system”

7. Enzymes Nomenclature “Systematic naming system”

8. Enzymes Properties: 1. Active site specificity
Each enzyme has a unique empty space within its structure named the active site
The active site contains amino acids portion that participate in the substrate interactions to form enzyme–substrate (ES) complex
This binding catalyzes the substrate via structural transformation

9. Enzymes Properties: 1. Active site

10. Enzymes Properties: 2. Catalytic efficiency
Efficiency is one of the most important properties of enzymes
When enzymes are not catalyzing a reaction, it takes 108 longer
The amount of byproduct that results from the catalytic reaction is called the turnover number
This number range between product per second

11. Enzymes Properties: 3. Coenzymes and Cofactors
Some enzymes can not facilitate a catalytic reaction with a substrate without the presence of certain molecules
When these molecules composed of metallic ions such as Zn2+ or Fe2+, it is called cofactors
On the other hand, if the extra molecules organic in nature it is denoted as coenzymes. E.g. vitamins B1

12. Enzymes Properties: 3. Location
Enzymatic reactions take place in specific location within a cell
This aspect of enzyme compartmentalization provide the specify of enzymes
Since there are thousands of enzymes within a cell, isolating enzymes from their substrates into specific organelles helps in organizing the huge number of pathways

13. Enzymes Properties: 3. Location

14. Enzymes Factors affecting rate of reaction 1. Substrate concentration
The velocity of the rate of reaction (V) is equal to “the number of substrate molecules converted to product per unit of time”
The of products produced keep forming is proportional to the substrate concentration
This increase in the rate enzymatic reaction is limited by the maximum velocity of the reaction and not the substrate concentration

15. Enzymes Factors affecting rate of reaction 1. Substrate concentration

16. Enzymes Factors affecting rate of reaction 2. Temperature
Until a maximum velocity is reached, the velocity of enzymatic reaction is increased as the temperature increases
This is due to the increase the amount of substrate complex having sufficient energy
Any further increase in the temperature will retard the rate of the reaction
The reason behind this is the denaturation of the enzyme

17. Enzymes Factors affecting the rate of reaction 1. Temperature

18. Enzymes Factors affecting the rate of reaction 3. pH
Reaction velocity is controlled by the concentration of (H+)
The catalytic activity of enzyme require the targeted chemical group to be in a specific ionized form
Similar to high temperature, extreme pH value can slow the rate of reaction due to the degradation of the enzyme itself
Each enzyme has preferred range of pH within the body

19. Enzymes Factors affecting the rate of reaction 3. pH

20. Enzymes Inhibition
Inhibitors are any substance that interfere with the enzymatic reaction
These inhibitors can be irreversible when it form a covalent bond, e.g. Lead binds covalently with ferrochelatase preventing heme synthesis
They can also be reversible when covalent binding is not a factor

21. Enzymes Reversible Inhibition
Reversible inhibition can be classified to either competitive or non-competitive inhibition
Competitive inhibitors occupy the site of the substrate
Non-competitive inhibitors bind to a different site form the substrate

22. Enzymes Reversible Inhibition
Competitive inhibition
Non-Competitive inhibition

23. Enzymes Clinical Applications
Different enzymes are released from different part of the body
The level of the enzyme in circulatory system can be correlated to a number of disease
Enzyme level in serum can be quantified and compared to normal levels
For example, the enzyme alanine aminotransferase (ALT) presence at high level in blood is an indication of liver disease

24. Enzymes Clinical Applications
Enzyme level in blood