ENZYMES Flashcards
• Papain/Papase
From papaya
fruit enzyme
• Bromelain
Pineapple
Used as meat tenderizer
Used for constipation
• Peptidase
cleaves polypeptide chains
• Proteolytic enzymes
Cleaves proteins in general
• Salivary Amylase
Digestion of starch
• Digestive enzymes
Chymotrypsin
Trypsin
Pepsin
pH of digestive enzynes
pH 2
Brain enzymes
Acetylcholinesterase
Monoamine oxidase
Liver enzymes
Alanine aminotransferase (ALT) Aspartate aminotransferase (AST)
Glucose-6 Phosphate Dehydrogenase
involved in glucose metabolism – glycolysis
part of newborn screening
Lactase
Breakdown of Lactose
Inadequacy leads to lactose intolerance meaning cannot breakdown lactose (milk) leading to diarrhea
Alcohol dehydrogenase and Aldehyde dehydrogenase
Detoxification of alcohol
Converts acetaldehyde to ethanol
Inadequacy can lead to low alcohol tolerance
Decarboxylase
Catalyzed decarboxylation
Decarboxylation is the chemical reaction involved in removal of carboxyl group while releasing carbon dioxide
Cardiac enzymes
Troponin and Creating Phosphokinase (CPK)
Lipase
breakdown of lipids
Antioxidant enzymes
Glutathione peroxidase
Glutathione reductase
Catalase
Catalase
Breakdown and detoxification of hydrogen peroxide (H2O2)
o protein part of an enzyme
apoenzyme
o non-protein portion of an enzyme that is necessary for catalytic function
• Cofactor
Examples of cofactors
Zn2+ and Mg2+ (inorganic compounds)
Without this cofactor will not make the enzyme functional
o non-protein organic molecule, frequently a B-vitamin, that acts as a cofactor
o on a different level
Energy-rich compounds
coenzyme
o compound/s whose reaction an enzyme catalyzes
• Substrate
o specific portion of the enzyme to which a substrate binds during reaction
Active site
Crevice or cleft of an enzyme
• Active site
site of reaction
Active site
any process that initiates or increases the activity of an enzyme
Activation
portion on the enzyme surface where inhibitors/activators bind to regulate catalytic reactions
Allosteric site
o where inhibitors can compete with the substrate to activate and regulate catalytic reactions
Allosteric site
compound/s that slows down the rate of the reaction
Inhibitors
process that makes an active enzyme less active or inactive
• Inhibition
Mechanism of Drugs
Enzyme Catalysis
Substrate-specific (stereoselective , site targeting)
Efficient
Enzyme Specificity
Reaction Specificity
o the ability of an enzyme to discriminate among possible substrate molecules
Enzyme specificity
o Highly specific for reactants/substrates SIZE AND SHAPE can mediate a chemical reaction.
Reaction specificity
Conformation or confirmation based on the presence of a particular amino acid.
Concepts of R groups, polarity, hydrophobicity
Stereoselective
Important because the active part of the enzyme is the active site.
Presence of inhibitors
Site targeting
o Can accelerate a reaction (109 - 1020)
Efficient
molecular species consisting of a substrate (S) bound to the active site of an enzyme (E)
Enzyme-substrate (ES) complex
Two scenarios in ES complex
Easy Fit
Enzyme would need to adjust
Transient product is formed if
during the scenario that enzyme slightly adjusted
transient - sandali lang
Transition state
when the activation energy has been OVERCOME and the products are formed leaving the active site of an enzyme
REMEMBER THAT
role of enzyme on formation of product
the enzyme does not participate thermodynamically in the formation of the product.
It just simply hastens the formation of product in the active site of the enzyme.
with that the enzyme CAN STILL BE RECOVERED
Doe NOT affect final product. it only acts as ACCELERATOR
Role of trypsin
Catalyzes the hydrolysis of peptide bonds formed by the carboxyl group of LYSINE and ARGININE
• The intermediate compound formed from the combining of catalysts with the substrate
Enzyme-substrate complex
Binding of the active site occurs through
NON-COVALENT INTERACTION
o Enzymes speed up a reaction by
LOWERING THE ACTIVATION ENERGY of a given reaction
the enzyme will help primarily the substate and enzyme to attain a transition state
rate of appearance of products or rate of disappearance of substrate
• Rate of a chemical reaction
(highest
point on an energy diagram of a
reaction)
Transition state
the necessary
amount of energy and the correct
arrangement of atoms to produce
products
highest amount of
energy required and there should be a
correct arrangement of atoms to produce
a product
Transition state
the amount of energy inputted and is
computed based on the exponent on the
rate equation
Order of reaction
– reaction that
proceeds at a constant rate and is
independent of reactant
Zero order
rate reacts on the
first power of the concentration of
a single reaction
First order
rate is
proportional to the products of the
concentration of the two reactants
Second order
No adjustments can be made in the conformation
Lock and key model mechanism
Active site becomes modified to accommodate the substrate
Induced fit model
Assumes small (minor) but continuous changes in the active site structures
Induced fit mode
active site is a rigid, inflexible 3D body
Lock and key model mechanism
Type of inhibitor: assembles the structure of normal substrate
and it’s capable of binding to the active site of the
enzyme
Competitive
Type of inhibitor: both the inhibitor and substrate can bind
simultaneously to two different sites on the enzyme
Noncompetitive
Type of inhibitor: allow substrate to bind the active site and or binds
only to the ES complex and not with the free
enzyme; thus, influencing the activity of the enzyme
only when the substrate concentration and, in turn,
ES concentration are high
Uncompetitive
Type of inhibitor: there is another site other than the active site that
the substrate can bind to and as well as inhibitor
Noncompetitive
Type of inhibitor: follows allosterism
Noncompetitive
an efficient
enzyme control mechanism because the entire series of
reactions can be shut down, when an excess of the final
product exists, thus preventing the accumulation of the
intermediary products (called intermediates) in the
pathway or sequence of reaction
Enzyme Regulation
What are the enzyme regulations
Feedback control
Proenzyme (Zymogen)
Allosterism
Also known as Feedback inhibition / End product
inhibition
Feedback control
An enzyme-regulation process where the product of a
series of enzyme-catalyzed reactions inhibits an earlier
reaction in the sequence.
Feedback control
Enzyme regulation wherein
The inhibition may be competitive or noncompetitive.
Feedback control
An inactive form of an enzyme that must have part of its
polypeptide chain hydrolyzed and removed before it
becomes active.
Proenzyme / Zymogen
Digestive enzymes / proteolytic enzymes that are initially produced as
zymogen
Trypsin / Trypsinogen
Chymotrypsin / chymotrypsinogen
It becomes active only after a six amino acid
fragment is hydrolyzed and removed from the end
terminal end of its chain. In so doing, removal of these
small fragments changes not only the primary structure,
but also the tertiary structure, allowing the molecule to
achieve its active form.
Type of inhibition that has NO CATALYTIC REACTION
Noncompetitive
Enzyme regulation based on an event occurring at a place
other than the active site but that creates a change in the
active site
Allosterism
An enzyme regulated by allosterism is called an
allosteric enzyme
Inhibition of an allosteric
enzyme
Negative modulation
Stimulation of an allosteric
enzyme.
Positive modulation
Process of affecting enzyme activity by COVALENTLY MODIFYING it
Protein modification
Causes a change in the primary structure through the
addition of a functional group covalently bound to the
apoenzyme
Protein modification
Enzyme that occurs in multiple forms that each catalyzes the
same reaction
ISOZYMES/ ISOENZYMES
• A molecule whose shape mimics the transition state of s
substrate
Transition state analogs
When they mimic, they can now be used as enzyme
inhibitors.
Transition state analogs
An antibody that has catalytic activity because it was
created using a transition state analog as an immunogen
Abzymes
This is the principle in making designer enzymes by
biotechnology molecular technology then you’ll be able
to prepare or make designer enzymes to be able to
catalyze various types or a wide variety of reactions
TRansition state analog (Abzymes?)
• Series of mathematical relationship that explains the
behavior of non-allosteric enzymes
Michaelis Menton Equation
Combination of zero order and 1st order kinetics
Michaelis Menton Equation
When S is low, the equation for rate is 1st order in S
• When S is high, the equation for rate is 0-order in S
describes the velocity of enzymes
catalyst reaction where there is saturating
level of the substrate
V max:
v max can be used to
determine the individual rate
constant but to a certain extent
What is KM
Michaelis constant
it is mathematically equal to the substrate
concentration that generates half of the
maximum velocity
Michaelis constant (KM)
Disadvantage of Michaelis-menton equation
you will be able to calculate now the velocity
given the substrate concentration but only to a certain
extent because there is a saturation point
The curve is hyperbolic compared to other graphs
which are sigmoidal. So it gives you a rectangular
hyperbolic dependency curve of the velocity on the
substrate
Michaelis constant equation
