This document discusses factors that affect enzyme activity such as temperature, pH, substrate and enzyme concentration. It also discusses extremophile enzymes (extremozymes) and how they are useful. Enzyme inhibition including competitive, noncompetitive and irreversible inhibition is explained. Examples of prescription drugs that inhibit enzymes like ACE inhibitors, sulfa drugs and penicillins are provided. Finally, the medical uses of enzymes in disease diagnosis, treatment and chemical analysis are briefly mentioned.

1. Chapter 4- Enzymes and Vitamins
(Part B of Enzymes)
JEMIMAH JOY I. GUARIN

2. Part B:
• Factors that affect enzyme activity
• Extremozymes
• Enzyme Inhibition
• Prescription Drugs that Inhibit Enzyme Activity
• Medical Uses of Enzymes

3. Factors that Affect Enzyme Activity
Enzyme activity- is a measure of the rate at which an enzyme converts the
substrate to products in a biochemical reaction.
• Temperature
• pH
• Substrate concentration
• Enzyme concentration

4. Temperature
temperature  molecules are moving faster and colliding more frequently.
temperature of an enzymatically catalyzed reaction;
the rate (velocity) of the reaction

5. Temperature
• Temperature increases beyond a certain point, and the increased energy begins to
cause disruptions in the tertiary structure of the enzyme  enzyme denaturation.
• Change in tertiary structure at the active site impedes catalytic
action, and the enzyme activity quickly decreases as the
temperature climbs past this point.
• Optimum temperature- is the temperature at which an enzyme
exhibits maximum activity.

6. Temperature
Example:
Human enzymes the optimum temperature is 37°C.
-If it exceeds 40°C, it can be a life-threatening situation because such a
temperature is sufficient to initiate enzyme denaturation.
Autoclaves- a high temperature, high-pressure vessels
Wherein super-heated stem is used to produce a
Temperature is sufficient to denature bacterial enzymes.

7. pH
• The pH of an enzyme’s environment can affect its activity.
• Small changes in pH can result in enzyme denaturation and subsequent loss of
catalytic activity.
• Most enzymes exhibit maximum activity over a very narrow pH range.
• Optimum pH- is the pH at which an enzyme exhibits maximum activity.
• Biochemical buffers help maintain the optimum pH for an enzyme.
• Enzyme physiological pH range: 7.0-7.5
• Exception: the digestive enzymes pepsin=2.0 ; trypsin=8.0
• A variation from normal pH can also affect substrates, causing either
Protonation or deprotonation of groups on the substrate.

8. Substrate Concentration
• Saturation curve- is when the concentration
of an enzyme is kept constant and the
concentration of substrate is increased.
• Each substrate must occupy an enzyme
active site for a finite amount of time, and
the products must leave the site before the
cycle can be repeated.
• Turnover number- is the number of substrate
molecules transformed per minute by one
molecule of enzyme under optimum
conditions of temperature, pH, and
saturation.

9. Enzyme Concentration
• The concentration of substrate in a reaction is much
higher than that of the enzyme.
• The greater the enzyme concentration, the greater
the reaction rate.

11. Extremozymes
• Extremophile
- is a microorganism that thrives in extreme environments,
environments in which humans and most other forms of life could not
survive.
-comes from the Latin words: extremus extreme; philia love
• The ability of extremophiles to survive under such harsh conditions is
related to the amino acid sequences present in the enzymes
(proteins) of extremophiles.

12. Extremozymes
Types of Extremophiles:
Acidophiles- optimal growth at pH levels of 3.0 or below.
Alkaliphiles- optimal growth at pH levels of 9.0 or above.
Halophiles- high salinity, a salinity that exceeds 0.2 M NaCl needed for growth.
Hyperthermophiles- a temperature between 80°C and 121°C needed to thrive.
Piezophiles- a high hydrostatic pressure needed for growth.
Xerophiles- extremely dry conditions needed for growth.
Cryophiles- a temperature of 15°C or lower needed for growth.

13. Extremozymes
-is a microbial enzyme active at conditions that would inactivate human enzymes
as well as enzymes present in other types of higher organisms.

14. Extremozymes
General approach in the development of commercially useful enzymes using
extremophile sources:
1. Samples containing the extremophile are gathered from the extreme
environment where it is found.
2. DNA material is extracted from the extremophile and processed.
3. Macroscopic amounts of the DNA are produced using the polymerase chain
reaction.
4. The macroscopic amount of DNA is analyzed to identify the genes present that
are involved in extremozyme production.
5. Genetic engineering techniques are used to insert the extremozyme gene into
bacteria, which then produce the extremozyme.
6. The process is then commercialized.

15. Enzyme Inhibition
Enzyme inhibitor- is a substance that slows or stops the normal catalytic function of
an enzyme by binding to it.
-Reversible competitive inhibition
-Reversible noncompetitive inhibition
-Irreversible inhibition

16. Reversible Competitive Inhibition
Competitive enzyme inhibitor
-is a molecule that sufficiently resembles an enzyme-substrate in shape and
charge distribution that it can compete with the substrate for occupancy of the
enzyme’s active site.
-It decreases enzyme activity.

17. Reversible Competitive Inhibition
-It is a reversible process because it is maintained by weak interactions (hydrogen
bonds, etc.).
-Competitive inhibition can be reduced by simply increasing the concentration of
the substrate.
Within a
fraction of a
second, the
complex
breaks up.
The empty
active site is
then for a
navailableew
occupant.
Substrate and
inhibitor again
compete for
the empty
active site.

18. Reversible Competitive Inhibition
• Antihistamines
-competitive inhibitors of
histidine decarboxylation.

19. Reversible Noncompetitive Inhibition
Noncompetitive enzyme inhibitor
-is a molecule that decreases enzyme activity by binding to a site on an
enzyme other than the active site.

20. Reversible Noncompetitive Inhibition
-Lowering the concentration of a noncompetitive inhibitor sufficiently does free up
many enzymes, which then return to normal activity.
Examples:
Heavy metal ions: 𝑃𝑃𝑃𝑃 2+
, 𝐴𝐴𝐴𝐴+
, 𝐻𝐻𝐻𝐻2+
-the binding site for these ions are sulfhydryl groups (-SH) located away from
the active site.
-Metal sulfide linkages are formed, an effect that disrupts the 2nd and tertiary
structure.

21. Irreversible Inhibition
Irreversible enzyme inhibitor
-is a molecule that inactivates enzymes by forming a strong covalent bond
to an amino acid side-chain group at the enzyme’s active site.
-do not have structures similar to the enzyme’s normal substrate.
-The inhibitor-active site is sufficiently strong.
-Enzyme is permanently deactivated.
Example:
The actions of chemical warfare agents (nerve gases) and organophosphate
insecticides.

23. Prescription Drugs that Inhibit Enzyme
Activity
• ACE Inhibitors- used to treat high blood pressure conditions as well as several
heart conditions
• Two well-known families of antibiotics:
Sulfa drugs
Penicillins

24. ACE Inhibitors
• Angiotensin-converting enzyme
• Angiotensin is an octapeptide hormone involved in blood pressure regulation.
• Angiotensin inactive form zymogen angiotensinogen
• ACE converts the inactive decapeptide zymogen to the active octapeptide form
(angiotensin) by cleaving 2 amino acids from the zymogen structure.

25. ACE Inhibitors
• This medications block the action of ACE in converting angiotensinogen to
angiotensin.
• The effect of this is a lower blood pressure.
• Lisinopril- heavily prescribed for treatment of moderately elevated blood pressure
conditions.
-1-carboxy-3-phenylpropyl derivative of the dipeptide Lys-Pro.

26. Sulfa Drugs
• Antibacterial activity of sulfanilamide  Gerhard Domagk in 1932.
• The first antibiotics in the medical field.
• Antibiotic- is a substance that kills bacteria or inhibits their growth.
-they inhibit specific enzymes essential to the life processes of the bacteria.
Example:
Sulfanilamide inhibits bacterial growth because it is structurally similar to PABA
(p-aminobenzoic acid).

27. Sulfa Drugs

28. Penicillins
• One of the most widely used antibiotics.
• Accidentally discovered by Alexander Fleming in 1928.

29. Penicillins
• It inhibits transpeptidase.
-an enzyme that catalyzes the formation of peptide cross-links
between polysaccharide strands in bacterial cell walls.
• Its unique action depends on 2 aspects of enzyme deactivation:
-structural similarity to the enzyme’s natural substrate
-irreversible inhibition
• Is highly specific in binding to the active site of transpeptidase.
• Acts as a very selective competitive inhibitor.

30. Penicillins
• Penicillin does not usually interfere with normal metabolism in humans because of
its highly selective binding to bacterial transpeptidase.
• Penicillin an extremely useful antibiotic.

31. Medical Uses of Enzymes
• Enzymes can be used to diagnose certain diseases.
example: Enzyme concentrations can be useful in obtaining information
about a heart attack (blood enzyme).

32. Medical Uses of Enzymes
• Enzymes can be used in the treatment of diseases.
example: Tissue plasminogen activator (TPA)
• Enzymes used for chemical analysis in the clinical laboratory.
example: Blood urea nitrogen test (BUN)