Enzymes

BIOCHEMISTRY SLIDES

1. ENZYMES DEFINITION Enzymes are proteins that function as biological catalysts. A catalyst is a substance that speeds up a chemical reaction but isn’t changed by the reaction. Enzymes catalyze all aspects of cell metabolism.

2. Enzymes are highly specific to the reactions they catalyze They alter or speed up the rates of chemical reactions that occur in a cell. They remain unchanged after a chemical reaction. They are affected by temperature. They are affected by pH. They catalyze reversible reactions . PROPERTIES OF ENZYMES

3. DISTRIBUTION Enzymes are not randomly distributed but are specifically located inside the cells for example Digestive Enzymes: (Pancreas and stomach) Glycosol : ( oxidation of glucose) Mitochondria TCA cycle

4. GROUPS OF ENZYMES THERE ARE SIX MAJOR GROUPS OF ENZYMES

5. ENZYME PORTIONS Enzymes are composed of: 1.APO ENZYME : Protein portion consisting of amino acid chains 2. CO- FACTORS  activate enzymes and are not protein parts . HOLOENZYME (conjugated enzyme) Both cofactors and apo enzymes help to form a conjugated enzyme called holoenzyme .

6. 3. SUBSTRATE AND ACTIVE SITE : Enzymes operate by binding to a substrate The catalytic (active) site is the portion of the enzyme where substrate binding occurs.

7. MECHANISM OF ENZYME ACTION 1 .THE LOCK-AND-KEY HYPOTHESIS It was suggested by Arrhenius that the shape of the Active Sites of Enzymes is exactly Complementary to the shape of the Substrate.

8. 2.INDUCED FIT MODEL A more recent model suggested by Daniel Koshland the   Induced-Fit Model. It states that the shape of Active Sites are not exactly Complementary, but  are changed according to the substrate molecules

9. FACTORS AFFECTING THE RATE OF ENZYME ACTIONS   1. TEMPERATURE Enzymes have an optimum temperature at which they work fastest. Up to the optimum temperature the rate increases Above the optimum temperature the rate decreases

10. 2 . pH Enzymes have an  optimum pH  at which they work fastest. For most enzymes this is about pH 7-8 but a few enzymes can work at extreme pH, such as protease enzymes in animal stomachs, which have an optimum of pH 1.

11. 3 . ENZYME CONCENTRATION As the enzyme concentration increases the rate of the reaction increases linearly At very high enzyme concentration the substrate concentration may become rate-limiting

12. 4 . SUBSTRATE CONCENTRATION As the substrate concentration increases, the rate increases because more substrate molecules can collide with enzyme molecules, so more reactions will take place

13. INHIBITION CAN BE EITHER COMPETITIVE OR NONCOMPETITIVE 1. COMPETITIVE INHIBITION: Competitive inhibition is the interruption of an enzyme's ability to bind to a substrate due to a different molecule binding to the active site.

14. 2. NON COMPETITIVE INHIBITION : Non competitive inhibitors are not similar to the substrate and they do not bind to the active site of the enzyme. They change the conformation of the active site.

15. ROLE OF ENZYMES IN THE BODY 1. DEGRADATION REACTIONS (CATABOLIC) 2. SYNTHESIS (ANABOLIC) 3. DIGESTION Enzymes are used for a wide variety of purposes, such as in digestion. 4.PROTECTION Enzymes are also used in protection against Pathogens. They can be used to destroy invading Microorganisms.