ENZYMES Flashcards
1
Q
ENZYMES
Definition and function
A
• Biologic catalysts
Hasten chemical reactions
2
Q
T or F
Enzymes are not consumed during the reactions
A
True
3
Q
T or F
Enzymes do not undergo a chemical change after the reactions
A
True
4
Q
MAIN ACTION OF ENZYMES
A
• Catalyze/interact with substrate to mediate/facilitate chemical reactions.
5
Q
Where are enzymes found?
A
Enzymes are found in the cells and tissues.
They are present only in the circulation at a limited level (low
level)
6
Q
T or F
TESTING FOR ENZYMES is NOT DIAGNOSTIC for a certain disease.
A
True
Purpose: For the doctors to be alerted as to which body part, cell/tissue has a problem.
7
Q
• Study of enzymes
A
ENZYMOLOGY
8
Q
Study of enzymes
We have to look for:
A
• Activity of Enzymes
• Chemical reactions they catalyze
• Clinical uses
9
Q
T or F
Enzymes do not undergo change.
A
True
10
Q
Enzvme + substrate =
A
enzyme-substrate complex
which produces a product and the enzyme
11
Q
During________ reaction, the enzyme will not be consumed and the form will not be changed
The intact enzyme bound to the substrate is still the same enzyme that was expelled after______ were formed.
It retains the same appearance before binding.
A
enzyme+substrate
products
12
Q
T or F
There will still be products formed even when there is no enzyme
A
True
13
Q
Y axis =
X axis =
A
Energy usage
Time required to produce a product
14
Q
Enzymes may recognize and catalyze:
A
a single substrate
a group of substrates that have specific functional groups
A group of substrates that have a particular type of bond
15
Q
TYPES OF ENZYME SPECIFICITY
A
Absolute
Group
Linkage
16
Q
Catalyze one type of reaction for a single substrate
A
Absolute
17
Q
Catalyze one type of reaction for all similar substrates
A
Group
18
Q
Looks for a specific functional group (amino group, carboxyl group, ester, etc. made into substrate)
A
Group
19
Q
Urease catalyzes only the hydrolysis of urea
A
Absolute
20
Q
Hexokinase adds a phosphate group to hexoses
A
Group
21
Q
Catalyze one type reaction for a specific type of bond
A
Linkage
22
Q
Chymotrypsin catalyzes the hydrolysis of peptide bonds (all types of protein) [not all, but they share the peptide bond]
A
Linkage
23
Q
Lock and Key Model
A
Emil Fisher in 1894
24
Q
= where the substrate binds to an
enzyme
A
ACTIVE SITE
25
The________is where the activators and the inhibitors bind (not the substrate)
Allosteric site
26
•______ promote the binding of the enzyme to the substrate.
•______ prevent the binding of the enzyme to the substrate
Activators
Inhibitors
27
________prevent, so they make sure the substrate doesn't bind to the active site.
The shape of the enzyme is changed so they could not bind.
Inhibitors
28
An________ makes the enzyme better at binding the substrate
allosteric activator
29
• The substrate and the active site are not the same, so they could not bind
• What's needed for them to bind is for the______ to bind to the allosteric site
activator
30
is an inhibitor of xanthine oxidase.
Allopurinol
31
In inflammation, as _______ act as inhibitors.
anti-inflammatory drugs
32
NOMENCLATURE OF ENZYMES
1. Substrate + -ase (not true to all)
2. Reaction it catalyzes
3. Enzyme Commission Nomenclature (E.C.)
33
Substrate + -ase (not true to all)
Examples
a. Lipid = lipase
b. Ester = esterase
c. Protein = protease
34
Reaction it catalyzes
Nomenclature Examples
a. Oxidation = oxidase
b. Reduction = reductase
c. Hydrolysis = hydrolase
d. Dehydrogenase = remove hydrogen atoms
e. Decarboxylase = remove carboxyl groups
35
Enzyme Commission Nomenclature (E.C.)
E.C. 1.1.1.21
Meaning of each digit
• 1st digit = class
• 2nd digit = subclass
• 3rd and 4th = serial number
36
T or F
All enzymes end with an -ase
False
Examples: pepsin, trypsin
• Angiotensin-converting enzyme
37
CLASSIFICATION OF ENZYMES
HILLOT
Hydrolases
Isomerases
Ligases
Lyases
Oxidoreductases
Transferases
38
T or F
ENZYMATIC REACTIONS
Can occur in both ways. There is a forward and reverse reaction, thats why the arrow points both ways.
True
39
All enzymes in this class can perform oxidation and reduction forward and reverse.
OXIDOREDUCTASES
40
Oxidation
Reduction
O - removal of H ion
R - acceptance of H ion
41
(removal of hydrogen from lactate)
This enzyme has a lactate substrate.
Lactate Dehydrogenase
42
• Transfer of functional groups other than hydrogen from one substrate to another
TRANSFERASES
43
(transfers amino group)
Substrate is aspartate
Aspartate Aminotransferase
44
• Hydrolysis of various bonds
• Addition of water to a bond resulting in bond breakage
Loss of substrate
HYDROLASES
45
• Catalyze the removal of groups from Substrates without hydrolysis or oxidation; the product contains double bonds or a ring
LYASES
46
Which type of enzyme makes a product that contains double bonds or a ring
Lyases
47
It breaks down a big molecule, WITH NO WATER INVOLVED.
Lyases
48
• Rearrange the functional groups within a molecule and catalyze the conversion of one isomer into another
ISOMERASES
49
• Catalyze the joining of two large molecules by forming a new chemical bond
LIGASES
50
LIGASES
• Accompanied by an
ATP-ADP interconversion
51
Acted upon by the enzyme
• Specific
Substrate
52
• Different form, but with the same action
Isoenzyme
53
Non-protein molecule
Helper of enzyme / promote enzymatic attachment to the substrate
Some enzymes require cofactor, some do not
Cofactor
54
Polypeptide portion
Inactive enzyme
Enzyme that requires a cofactor BUT has not met a cofactor
Apoenzyme
55
Apoenzyme + Coenzyme
Enzyme that has met a cofactor
Holoenzyme
56
Holoenzyme
Apoenzyme + Coenzyme
57
Some enzymes require cofactors
Without cofactors:
With cofactors:
inactive apoenzyme
active holoenzyme
58
COFACTORS
TWO TYPES
Activators
Coenzymes
59
-› inorganic substances
Does NOT contain carbon
-› organic substances
• Contains carbon
Activators
Coenzymes
60
cofactors based on their binding tightness.
Prosthetic groups
Coenzymes
61
: Tightly bound
: loosely bound
Prosthetic groups
Coenyzmes
62
Metal ions (activators) or organic molecules
Change to the configuration of the enzyme/link substrate to the enzyme/ coenzyme
Copper is a member
Activators are members
Prosthetic groups
63
Organic molecules
"Second substrate" for enzyme reactions
Coenyzmes
64
Some enzymes require a_____ to facilitate the reaction.
The_______ binds the coenzyme and then the substrate.
The coenzyme is a part of the catalytic domain and will either donate or accept functional groups, allowing the reaction to occur.
Once the product is formed, both the_____ and _____ are released.
coenzyme
apoenzyme
product and the coenzyme
65
• Role: enzyme precursor / immature enzyme
Proenzyme/ Zymogen
66
There are certain enzymes, most especially digestive enzymes, they express as a ______
Proenzyme/ Zymogen
67
Not all enzymes have_____ - there are enzymes where once they are created, they are good to go.
proenzymes
68
is the proenzyme, whereas trypsin is the active enzyme.
Trypsinogen
69
ENZYME KINETICS
MICHAELIS-MENTEN THEORY
70
MICHAELIS-MENTEN THEORY
Leonor Michaelis
1875-1949
Maud Menten
1879-1960
71
MICHAELIS-MENTEN THEORY how many steps?
2
72
2 steps in MICHAELIS-MENTEN THEORY
First: forms non-covalent ES complex
Second: end in with a Product and Enzyme
73
• A double-reciprocal plot of the Michaelis-Menten constant which yields a straight line
LINEWEAVER-BURK PLOT
74
Presents the same thing as with the Michaelis-Menten Plot (MM Plot), the difference between the 2 is that the lineweaver-burk plot (LB Plot) presents a______ compared to the_____ of Michaelis-Menten's plot.
STRAIGHT LINE
HYPERBOLA
75
• Another difference is the unit of X and Y axis of the lineweaver-burk plot is the_____ of Michaelis-Menten which are the Velocity and Substrate concentration
RECIPROCAL
76
FACTORS THAT INFLUENCE ENZYMATIC REACTIONS
These factors either INCREASE or DECREASE the rate of reaction
Substrate concentration
Enzyme concentration
pH
Temperature
Cofactors
Activators
Inhibitors
77
Are those which proceed at a rate exactly proportional to the concentration of ONE
REACTANT
In enzymes, when the reaction rate is directly proportional to the substrate concentration
First-Order Reactions
78
Are those in which the rate is proportional to the product of the concentration of TWO REACTANTS or THE SQUARE OF THE CONCENTRATION OF ONE REACTANT
• Second-Order Reactions
79
Similarities between 1ST and 2ND order is that the relationship between SUBSTRATE conc. and VELOCITY is…
DIRECTLY PROPORTIONAL. (S = V | 1S ^V)
80
The MORE substrates you add, the FASTER is the______.
Which is true because if there are substrates, there are products nga form.
velocity
81
When the substrate concentration is high enough to saturate all available enzymes
• Zero-Order Reactions
82
A higher concentration of substrate will no longer result in increased reaction rate
• 1S = No change in V
• Zero-Order Reactions
83
• The HIGHER the enzyme level, the FASTER the reaction will proceed.
ENZYME CONCENTRATION
84
Once the reaction has reached its Vmax it cannot anymore produce any reaction but when enzyme is added the reaction will proceed once again eliminating Vmax-
ENZYME CONCENTRATION
85
Optimal pH
7.0-8.0
86
Changes in pH may____ the enzyme.
DENATURE
87
TEMPERATURE
•_____ is the OPTIMAL temp for enzymes
37° C
88
• Denaturation @
• Inactivation @
40-50°C (HOT)
4-10°C (COLD)
89
Assay temperatures:
25, 30, or 37°C
90
(Activators or Coenzymes)
• Non-protein entities that must bind to particular enzymes before a reaction occurs
COFACTORS
91
Cofactors
: Metallic or Nonmetallic
: Nucleotide phosphate and
Vitamins
Activators
Coenzymes
92
• Proper substrate binding
• Link substrate to the enzyme or coenzyme
• Undergo oxidation or reduction
ACTIVATORS
93
• Interfere with enzyme reactions
INHIBITORS
94
• 3 types of Inhibition
Competitive
Noncompetitive
Uncompetitive
95
: The inhibitor will bind to the ACTIVE SITE
Competitive Inhibition
96
: The inhibitor will bind to the ALLOSTERIC SITE.
Noncompetitive Inhibition
97
: The inhibitor will bind to the ENZYME-SUBSTRATE COMPLEX.
Uncompetitive Inhibition
98
The STRUCTURE of the substrate is
COMPLEMENTARY to the size and appearance of the active site.
So when they interact they will just merge as one perfectly.
LOCK AND KEY THEORY
99
According to one journal, this theory is too perfect, too good to be true. They believe that our body is not THIS PERFECT.
Lock and Key theory
100
There is a CLASH between the structure of the substrate and the active site of the enzyme.
If a substrate comes close to its target enzyme, the active site will CHANGE ITS STRUCTURE to accommodate the substrate
The fact the substrate is CLOSE TO THE ACTIVE SITE, is enough to change the structure of the active site to accommodate the substrate.
Induced fit theory
101
In the laboratory we do not measure the enzymes directly, but we measure their________; By measuring that, we will now come up with their______.
ACTIVITY
concentration
102
MEASUREMENT OF ENZYME ACTIVITY
• Increase in PRODUCT concentration.
• Decrease in SUBSTRATE concentration
• Decrease or increase in COENZYME concentration
• An increase in the concentration of the altered coenzyme
103
ENZYMATIC ASSAYS
1. Coupled- Enzyme Assay
2. Fixed - Time Method (End point)
3. Continuous - Monitoring Method (Kinetic Assay)
104
• Coupling the activity of the enzyme being tested to another, more easily detectable, enzyme
Coupled- Enzyme Assay
105
Measured here is the activity of
ANOTHER ENZYME.
This is because enzymes are difficult to catch or measure directly, so we need to examine another thing, in order to
represent our TARGET ENZYME.
Coupled- Enzyme Assay
106
•______ meaning you are using
MANY ENZYMES.
• Indirect measurement
Coupled-Enzyme
107
• Reactants are combined
• Reaction proceeds for a designated time
• Reaction is stopped
• Measurement is made of the amount of reaction that has occurred.
Fixed - Time Method (End point)
108
We are given with only 1 RESULT; meaning the measurement will only come at the
Fixed - Time Method (End point)
109
Multiple measurements of absorbance change
In order for us to know if there are
fluctuations in the absorbance while the machine is assessing your sample.
Continuous - Monitoring Method (Kinetic Assay)
110
CALCULATION OF ENZYME ACTIVITY
IU
IU/L
KATAL UNIT (mole/s)
111
• Amount of enzyme that will catalyze the reaction of 1 MICROMOLE OF SUBSTRATE PER MINUTE under specified conditions
INTERNATIONAL UNIT (IU)
112
Enzyme concentration
Used MOSTLY in the hospitals in the laboratory.
INTERNATIONAL UNIT PER LITER (IU/L)
113
• Amount of enzvme that will catalvze the reaction of 1 MOLE OF SUBSTRATE PER SECOND under specified conditions.
KATAL UNIT (mole/s): Sl unit
114
Is it normal for enzymes to be at an increased numbers in the circulation?
No
115
ALT (alanine transaminase) is found in the cells of the____.
liver
116
Enzyme + substrate = enzyme-substrate complex which produces a…
product and the enzyme
117
The Allosteric site is where the ____ and _____bind
activators and the inhibitors
118
1. Lipase with water will break down TAG (triacylglycerol.)
2. It will become…
Diacylglyercol with 1 Free Fatty Acid
119
○ Enzyme is strained
○ Product should always contain either a double-bond or a ring.
Lyase
120
Phosphoglycerate mutase is what type of enzyme?
Isomerase
121
Inactive enzyme
Apoenzyme
122
It binds and changes the active site
Cofactor
123
T or F
Copper is a coenzyme
False. It is inorganic therefore it is an activator
124
There are certain enzymes, most especially_____ enzymes, they express as a proenzyme
digestive
125
ALP → Has a pH:
9
126
ALP → Has a pH:
9
127
T or F
Each enzyme operates within a specific pH range
True
128
How to ensure desired pH in reagents?
- The Reagent box contains_____. It ensures desired pH is followed; NO MORE MANUAL measurement.
BUFFERS
129
End product of lyases contain
Double bonds
