Enzymes Protein molecules that act as catalysts Catalysts

Enzymes Protein molecules that act as catalysts

Catalysts § § § Speed up the rate of reactions Are not permanently changed or used up Reactants: what the catalysts change § To the right is a Scanning Electron Microscope image of rutile crystals grown using Altair's process.

Jobs enzymes do § § Join monomers to make polymers Break down polymers Phosphorylate molecules Bring atoms together so they can trade electrons § What kind of bonding is this? § polypropylene can be widely found in items such as plastic bottles and boxes, dishwashersafe food containers, patio furniture, rope, upholstery, diapers, and carpeting. § It did not become commercially viable until a catalyst that increased its production could be found

Naming enzymes § Depends on substrates and kinds of reactions § Nearly all enzymes end in “Ase” § Polycarbonate seen under a microscope

Activation energy § Adding energy to a substance makes it more reactive § For different reactions different energy thresholds are needed § Enzymes lower that threshold

Enzyme substrate complexes § Functional groups determine an enzyme’s shape § The part the substrate binds to is the active site § It looks like a pocket or groove § This means that an enzyme is very specific

Helper molecules § Some enzymes need to contain an additional molecule or ion to do their job § Cofactors are helpers held on by ionic or other kinds of bonds § Coenzymes are non-protein organic molecules § Like vitamins § They don’t get used up so we don’t need too many

Factors that effect enzyme activity § Vmax this is the fastest number of substrates an enzyme can process § Competitive inhibitors: look like the enzymes substrate so they block up the active site § More substrate can reduce their effects

Factors that effect enzyme activity § Noncompetitive inhibitors: effects don’t reverse § Cyanide, prevents Iron from doing its job in breathing § That’s why its fatal

Allosteric enzymes § Have 2 or more binding sites § Binding to a regulatory site changes the shape of the inactive enzyme, either stimulating or inhibiting enzymatic reaction

from Drug Discovery Today 11 481 -493 (2006)

“statins” Inhibitors of the enzyme HMG Co. A reductase The first enzyme in the pathway that makes cholesterol

Metabolic syndrome a combination of medical disorders that increase one's risk for cardiovascular disease and diabetes. Leads to 1. Obesity, particularly around the waist (having an "apple shape") 2. Elevated blood pressure 3. An elevated level of triglycerides and a low level of high-density lipoprotein (HDL) — the "good" cholesterol 4. Resistance to insulin

Complex interplay between glucose/fat/cholesterol metabolism

Enzymes? u. Biological washing powders u. Drug targets u. Tests for disease/test kits u. Clinical tests for liver damage

Biological washing powders Contain lipases and proteases to digest fat and protein in stains Work at lower temperatures

Energy and Enzymes Life requires energy. Almost all energy for life is derived from the sun. A “factoid” The sun’s energy that strikes Earth each day is equivalent to one million Hiroshima-sized atomic bombs. Photosynthesis harnesses about 1% of that energy – 10, 000 “atomic bomb equivalents” per day.

Chemistry and Life One unromantic but productive way of viewing life is to see it as a set of coordinated chemical reactions. This leads to an obvious question – What determines what chemical reactions are possible?

Chemical Reactions Whether a chemical reaction will or won’t occur under particular conditions is determined by the laws of thermodynamics. Keeping it simple If the overall amount of order is decreased by a reaction, the reaction is favored. Generally, if energy is released in a reaction, the reaction is favored.

The Direction of Spontaneous Reactions (and what it takes to go the other way)

Life Requires Lots of Unfavorable Reactions – How Is This Possible? By coupling favorable to unfavorable reactions. favorable reactions unfavorable reactions

The “Nature of Life” – Coupling Favorable to Unfavorable Reactions

ATP - Life’s Energy Currency Energy is released when ATP is hydrolyzed (broken down) to ADP. ATP is restored from ADP and an input of energy. ATP’s energy is used to drive endergonic (energy -requiring) reactions.

The Way ATP Often Works

Enzymes Speed Biochemical Reactions Enzymes are biological catalysts – substances that speed a reaction without being altered in the reaction. Most enzymes are proteins, some are RNA. Enzymes are essential for life. Model of the surface of an enzyme.

Enzymes Lower a Reaction’s Activation Energy

Enzyme Action

The Fit Between Enzyme and Substrate is Critical and Precise Hexokinase, an enzyme (blue), binding its substrate, glucose (yellow).

Many Enzymes Work by Altering the Shape of Their Substrates The active site of an enzyme is where substrate is bound.

Enzyme Deficiency and Health Most genetic disorders are due to a deficiency in enzyme function. This archival photo shows three children with the enzyme deficiency that causes phenylketonuria.

Metabolic Pathways The synthesis of biological molecules often requires many enzyme-catalyzed steps. The entire set of steps is a metabolic pathway.

Metabolic Pathways The metabolic pathway that produces tryptophan – an amino acid. This is one of hundreds of metabolic pathways essential for life.

Enzyme Activity is Often Regulated Feedback inhibition - a common form of enzyme regulation in which the product inhibits the enzyme.