Biology (enzymes)

Enzymes

Enzymes

hardest working protein you'll ever meet

- these are proteins (C-H-O-N). Proteins are macromolecules which are polymers of molecules called amino acids

- enzymes belong to the tertiary and quaternary structures

-NH2 (amine group) and the C=OOH (carboxylic group)

What do Enzymes Do?

- they are catalysts that speed up the chemical reactions that take place in cells

- lowers activation energy required for chemical reaction

How do Enzymes work?

- for a chemical reaction to proceed, there must be enough energy and collision. Enzymes provide a site for a reaction to proceed

- enzymes catalyze reactions by weakening chemical bonds which lower activation energy (min. energy required)

- lowering it has a dramatic effect how quick the reaction is completed.

characteristics of enzymes

1. Each enzyme has a unique 3D shape, including a surface groove called active site.

2. The enzymes works by binding a specific chemical reactant (substrate) to its active site, causing the substrate to become unstable and react. This creates an enzyme-substrate complex.

3. Resulting products is then released from the active site.

• Enzymes are specific for what they will catalyze

• Enzymes fit substrate like a lock and key. One enzyme is to one substrate.

Emil Fischer

- described the complex as a lock and key model

75, 000 enzymes recorded-- some of which are:

• Metabolic enzymes • Digestive enzymes • Food enzymes

enzymes are reusable. They are not consumed (use up) in the reactions they catalyze enzymes are like tiny machines within living things the more substrate, the more products

Why are Enzymes so important?

- nearly all chemical reactions in biological cell need enzymes to make the reaction occur fast enough to support life

How do you stop an enzyme?

denaturing is the alteration of a protein shape through some form of external stress. When the shape of an active site changes as a result of bonds within the enzyme breaking. ex. applying heat or changing pH - denatured protein can't carry out its cellular function

Factors that affect Enzyme Activity

Temperature

pH

Inhibitors

Cofactors and Coenzymes

Temperature

- far above the normal range denature enzymes

- this is why very high fevers are so dangerous, they can cook the body's proteins. They may cause convulsions.

- those enzymes produced by human cells generally work best at temperature close to 37oc, the normal temperature of the human body.

- for example, by cooking the egg, you denature its albumins, globulins, and muco proteins. Under intense heat, Hbonds that formed during its secondary structure break- lose their shape and change function.

pH

-at very acidic and basic pH values the shape of the enzyme is altered so that it is no longer complementary to its specific substrate.

- enzymes work best at certain ionic conditions and pH values

- only at optimal pH.

- Pepsin is an enzyme in gastric juices that digest proteins, works best under acidic conditions

Cofactors and Coenzymes

- non-protein substances (zinc, iron, copper, vitamins) are sometimes needed for proper enzymatic activity.

3.1 Cofactor

3.2 Coenzyme

- more general term. Includes organic and inorganic molecules. Cofactors do not bind the enzyme. Cofactors are "helper molecules" and can be inorganic or organic in nature.

- type of cofactor, but specifically organic molecules (vitamin a to z). Coenzymes are organic molecules and quite often bind loosely to the active sit of an enzyme and aid in substrate recruitment

Inhibitors

molecules that interact in some way with the enzyme to prevent it from working in the normal manner - most medicines use the enzyme and inhibitor mechanisms

Competitive Inhibitors

- chemicals that resemble an enzyme's normal substrate and compete with it. for the active site.

- reversible depending on the concentration of inhibitor and substrate.

Non-competitive inhibitor

- do not enter the active sit but bind to another part of the enzyme, causing the enzyme and active site to change shape.

- binds to the allosteric site

- any site on the enzyme aside from the active site; still changes the shape of the active site

- usually reversible, depending on concentration of inihibitor and substrate

Catecholase

- is present in most fruits and vegetables

- facilitate the browning of cut and bruised fruits and vegetables by catalyzing the following reaction: catechol + oxygen ------> polyphenol

Bromelain

- is a protease enzyme that facilitate hydrolysis of preotein

- hydrolysis cuts molecule by adding water collagen protein + H2O --> amino acids

- proposed as muscle medication, but not yet approved.

Classification of Enzymes

1. Oxidoreductase

2. Transferases

3. Hydrolases

4. Isomerases

5. Lyases

6. Ligases (synthetases)

Oxidoreductase

- transfer of H and O atoms or electrons from one substrate to another

ex. dehydrogenases and oxidases

transferases

- transfer of a specific group from one substance to another

ex. transaminase and kinases

Hydrolases

- hydrolysis of a substance

ex. estrases and digestive enzymes

Isomerases

change of molecular form of the substrate

ex. phospo hexo isomerase and fumarase

Lyases

non hydrolytic removal of a group or addition of a group to a substrate

ex. decarboxylases and aldolases

Ligases (synthetases)

joining of 2 molecules by the formation of new bonds

ex. citric acid and synthetase