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
substrate
inhibitor
competitive inhibition
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
substrate
inhibitor
non-competitive inhibition
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 CoA 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?
Biological washing powders
Drug targets
Tests for disease/test kits
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?
favorable
reactions
By coupling favorable to
unfavorable 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 .