What Are Enzymes?What Are Enzymes?

• An enzyme is a catalyst in cellular reactions.

• DEFINE catalyst

• Enzymes are protein or nucleic acids with ((tertiary and quaternary structure).

EnzymesEnzymes

• have specificity

• Are reusable

• End in -ase-Sucrase-Sucrase-Lactase-Lactase-Maltase-Maltase

• Chemical reactions control all of the chemical compounds in our body allowing us to move, grow, react, and even reproduce.

• Parts of a chemical reaction:

Reactants ------------> Products

The sum of all of the chemical reactions that occur in our bodies is called

metabolism.

Chemical reactions in which molecules are broken done and release energy; degradation

•Example: Hydrolysis

Catabolism

Chemical reactions in which molecules are assembled, usually they require energy; synthesis

•Example: Dehydration Synthesis

Anabolism

Metabolism

• the sum of all chemical reactions with a living organism

catabolism + anabolism = metabolism

Why do we need enzymes?

ENZYMES!• Reactants ------------> Products

• Enzymes catalyze the chemical reactions in our body

What is lactose intolerance then?

How do enzymes work?The Enzyme-Substrate Complex

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

• The enzyme works by binding a specific chemical reactant (substrate) to its active site, causing the substrate to become unstable and react.

• The resulting product is then released from the active site.

How Do Enzymes Work?How Do Enzymes Work?

Enzymes work by weakening bonds which lowers activation energy.

Active SiteActive Site

EnzymeSubstrate

Active Site

Shape of a Protein ...Structure Meets Function

• An enzyme fits with its substrate like a ____ and ____.

• Enzyme have specificity.

4 levels of Protein Structure

How important is the shape of an enzyme?

• Which substrate would be catalyzed by this enzyme?

How Do You Stop an Enzyme?

Irreversible egg protein denaturation caused by high temperature (while cooking it).

Denaturation:

• The process of changing the shape of a enzyme thus destroying its function

•Caused by heat or pH

Factors Affecting Enzyme Activity

• Temperature

• pH

• Cofactors & Coenzymes

• Inhibitors

Coenzymes & Cofactors

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

Example of enzyme cofactor : Ribbon-diagram showing carbonic anhydrase II. The grey sphere is the zinc cofactor in the active site.

Catecholase

• Catecholase is present in most fruits and vegetables.

• It is the enzyme that facilitates the browning of cut or bruised fruits and vegetables by catalyzing the following reaction:

(catecholase)

catechol + oxygen ----------------- polyphenol colorless substrate brown product

So what happened to the apple slice?

Lemon juice and other acids are used to preserve color in fruit, particularly apples, by lowering the pH and removing the copper site (cofactor)necessary for the enzyme to function.

catecholasecatechol + O2 -------------------------- polyphenol

colorless substrate brown product

• So what happens to catecholase when you add an acid (lemon juice) to the apple slice?

Two Types of Enzyme InhibitorsTwo Types of Enzyme Inhibitors

1. Competitive inhibitors:1. Competitive inhibitors: Chemicals that resembleresemble an enzymeenzyme’’s normal s normal

substrate substrate and competecompete with it for the active active sitesite.

Example: Methotrexate is used in chemotherapy and inhibits an enzyme involved in DNA replication (a process necessary for cell division)

Substrate

Two Types of Enzyme InhibitorsTwo Types of Enzyme InhibitorsNoncompetitive inhibitors:Noncompetitive inhibitors:

Do not enter the active siteo not enter the active site, but bind to bind to another part another part of the enzymeenzyme causing the enzymeenzyme to change its shapechange its shape, altering the altering the

activeactive sitesite. Substrate

active site altered

Enzyme InhibitorsEnzyme Inhibitors

Blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance.

Many drugs are enzyme inhibitors.

Enzymes are also used as pesticides and herbicides.

Overview of Mammalian Digestive Enzymes