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CC2 LECTURE > C1 - Section 1. INTRODUCTION TO ENZYMES > Flashcards

C1 - Section 1. INTRODUCTION TO ENZYMES Flashcards

1
Q

is a field of laboratory medicine which focuses on the study of enzymes and their significance to the diagnosis and treatment of diseases.

A

Clinical Enzymology

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2
Q

These are substances that catalyzes a given chemical reaction

A

enzymes?

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3
Q

The reaction they catalyze are frequently (?) which means which means that they can synthesize and decompose molecules

A

reversible

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4
Q

They are (?) types of protein in terms of both structure and function

A

complicated

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5
Q

They easily (?) with varying molecular weight and mass

A

denatured

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6
Q

These enzymes are (?) which are capable of ionizing either as acid or base

A

amphoteric

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7
Q

They are synthesized in an (?) and operates in the presence of a (?)

A

inactive state

cofactor

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8
Q

Enzymes are found in all body tissues, they appear in the serum following cellular injury or they may come from degraded cells thus changes in (?) reflects changes in state of health.

A

enzyme concentration

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9
Q

non-protein organic biochemical that takes part in the enzyme reaction

A

Coenzymes

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10
Q

Essential to the catalytic activity as a CO-SUBSTRATE

A

Coenzymes

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11
Q

Diffusible, heat stable, low molecular weight that when combined tightly to enzymes, the coenzyme will be called Prosthetic group

A

Coenzymes

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12
Q

Coenzymes E.g.

A

NAD, Pyridoxal phosphate

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13
Q
  • Inorganic ionic cofactor
A

Activators

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14
Q

increase the catalytic activity of an enzyme when it binds to specific site

A

Activators

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15
Q

Metabolic regulator of enzyme reaction

A

Activators

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16
Q

Usually metal ions (esp. divalent cations)

A

Activators

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17
Q

Activators E.g.

A

Mg++, Na+, K+, Zn++

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18
Q
  • the combined enzyme & coenzyme
A

Holoenzyme

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19
Q
  • Enzyme without a cofactor
A

Apoenzyme

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20
Q
  • A coenzyme that cannot be removed from its attachment to an enzyme using dialysis
A

Prosthetic Group

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21
Q

Prosthetic Group E.g.

A

Pyridoxal phosphate in transaminase reaction

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22
Q
  • Substance acted upon by an enzyme & is converted into a new substance
A

Substrate

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23
Q
  • Substance derived from a transformed substrate
A

Product

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24
Q

– Site where substrate interacts with enzymes

A

Active site

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25
Q

– Site other than the active site that may lead to either attachment of substrate to the enzyme’s active site or inhibition of attachment

A

Allosteric site

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26
Q

– different form of an enzyme with different genetic origins but catalyze the same reaction

A

Isoenzymes

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27
Q

– Results when an enzyme is subject to different post-transitional modification

A

Isoforms

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28
Q
  • Refers to the sequence of amino acids joined by peptide bonds to form a polypeptide chain
A

a. Primary Structure

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29
Q
  • Conformation of the segments of polypeptide chain
A

b. Secondary Structure

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30
Q

Made up of alpha helices or beta-pleated sheets which are maintained by hydrogen bonds

A

b. Secondary Structure

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31
Q
  • Arises from the interactions among side chains/groups of the polypeptide chain
A

c. Tertiary Structure

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32
Q

Structure are bent and folded and maintained by covalent disulfide bond

A

c. Tertiary Structure

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33
Q
  • Separate bended & folded structures are put together to form a functional unit
A

d. Quarternary Structure

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34
Q

Enzyme variants –

A

LDH, Creatine kinase

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35
Q

The enzyme action model
a. Enzymes act through formation of (?)
b. The substrate must be bound to the (?)
c. The (?) will then break down to give the reaction products and free the enzyme
d. All enzyme reactions are in theory (?) however, in practice, reactions are usually more rapid in one direction than the other.

A

enzyme substrate complex

active site of the enzyme

enzyme-substrate complex

reversible

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36
Q

refers to the active site being complementary in shape & size to the substrate

A
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37
Q

First presented by Emil Fisher, the lock represents an enzyme and the key represents a substrate.

A

Lock and Key Theory

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38
Q

It is assumed that both the enzyme and substrate have fixed conformations that lead to an easy fit.

A

Lock and Key Theory

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39
Q

Because the enzyme and the substrate are at a close distance with weak attraction, the substrate must need a matching shape and fit to join together.

A

Lock and Key Theory

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40
Q

At the active sites, the enzyme has a specific geometric shape and orientation that a complementary substrate fits into perfectly.

A

Lock and Key Theory

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41
Q

Factors that influence the enzymatic reaction

A
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42
Q

– The rate of enzymatic reaction

A

Time

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43
Q

If the catalytic activity of an enzyme on a substrate is fast, this will mean a shorter reaction time thus liberating the enzyme to act again on the remaining substrate

A

Time

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44
Q

– Commonness between the enzyme and the substrate

A

Molecular compatibility

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45
Q

– Number of substrate that can be reacted

A

Space availability

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46
Q
  • capacity of enzymes to recognize and bind only one or few molecules among others
A

Specificity

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47
Q

– when an enzyme can act and catalyze one unique reaction

A

Absolute specificity

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48
Q

– when some enzymes act on different substrates belonging to the same group

A

Group specificity

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49
Q

– an enzyme acts only on the specific isomer

A

Stereoisomeric

50
Q

o Enzyme conc. is fixed; Substrate conc. is varied

A

First order Kinetics

51
Q

o Rate of reaction is almost directly proportional to substrate conc. at low values

A

First order Kinetics

52
Q

o At low concentration of the substrate, only a fraction of the enzyme is associated with the substrate

A

First order Kinetics

53
Q

o The rate observed reflects the low concentration of the ES complex

A

First order Kinetics

54
Q

o When maximum velocity is reached, the rate of increase in velocity is “O”

A

Zero order Kinetics

55
Q

o Reaction rate is unaffected by increased substrate concentration

A

Zero order Kinetics

56
Q

o Dependent on enzyme concentration

A

Zero order Kinetics

57
Q

o In this reaction, the entire enzyme is bound to substrate and a much higher rate of reaction is obtained

A

Zero order Kinetics

58
Q

o Because the entire enzyme is present in the form of the complex, there is now no further increase in ES complex conc. No further increment in reaction rate are possible

A

Zero order Kinetics

59
Q
  • shows the relationship of the reaction velocity to the substrate concentration
A

Michaelis-Menten Curve

60
Q
  • °T considered favorable for enzyme activity (30-37°C or 37 – 40°C)
A

Optimum temperature

61
Q

– reaction rate is doubled for every 10°C increase

A

Q10 value

62
Q

: enzyme undergoes inactivation and denaturation

A

50 – 60°C

63
Q
  • the point at w/c the reaction rate is greatest
A

Optimum pH

64
Q

, many enzymes show maximum activity

A

At pH 7.0 – 8.0

65
Q

pH value are seen as

A

low as 1.5 and as high as 10.5

66
Q

may be different in forward and reverse reaction

A

Optimal pH

67
Q

is important: it affects the three dimensional confirmation of the enzyme

A

Maintaining pH

68
Q

– increased reaction rate

A

Activators

69
Q

Bind the substrate to the active site by forming ionic bridges

A

Activators

70
Q

Orients the substrate so it is attached to the enzyme in the correct configuration

A

Activators

71
Q
  • Decrease the rate of enzyme reaction
A

Inhibitors

72
Q
  • Inhibitors Binds to the active site, blocks access of the S to the E
A

Competitive inhibition

73
Q

is a structural analog of the substrate, but it is not identical thus breakdown to products do not take place o

A

competitive inhibitor

74
Q

If substrate conc. Is significantly higher than the inhibitor, the inhibition may be reversible

A

Competitive inhibition

75
Q
  • Binds elsewhere on the E causing change in shape that interferes w/ S binding
A

Non-competitive inhibition

76
Q

Attachment of the inhibitor to the enzyme does not alter the affinity but the presence of ESI prohibit the formation of products

A

Non-competitive inhibition

77
Q
  • Inhibition-inhibitors binds to the ES complex, if substrate will be increased, there will be increase in ES conc. increasing inhibition, this inhibition does not yield product.
A

Uncompetitive inhibition

78
Q
  • Inhibitors are possible removed from the system; enzyme is fully restored
A

Reversible inhibition

79
Q
  • Inhibitors covalently combine w/ the enzyme
A

Irreversible inhibition

80
Q

o Physical methods are ineffective in separating inhibitors from the enzymes

A

Irreversible inhibition

81
Q

o Physical processes that remove inhibitors: dialysis, gel filtration

A

Reversible inhibition

82
Q

Methods of Enzyme Assay

A
83
Q

The reactants are combined

A

Fixed Timed Assays

84
Q

Reaction proceeds for a designated time & is stopped (by inactivating the enzyme)

A

Fixed Timed Assays

85
Q

reaction is stopped by a weak acid, then measurement is made of the amount of reaction that has occurred

A

Fixed Timed Assays

86
Q

The reaction is assumed to be linear over the reaction time, the larger the reaction, the more enzyme is present

A

Fixed Timed Assays

87
Q

Multiple measurements are made at specific time intervals or by a continuous-recording spectrophotometer

A

Continuous-monitoring or kinetic assay

88
Q

Advantage: Linearity of the reaction is adequately verified

A

Continuous-monitoring or kinetic assay

89
Q

This is preferred because any deviation in linearity is readily observable

A

Continuous-monitoring or kinetic assay

90
Q

Proposed by the Commission on Enzymes (IUB)

A

IU – International Unit

91
Q

Used to standardize the system or reporting of quantitative results

A

IU – International Unit

92
Q

is the amount of enzyme that will catalyze the reaction of 1 µmol of substrate per minute under specified conditions of temperature, pH, substrate and activators.

A

IU – International Unit

93
Q

Expressed in terms of U/L or mU/L

A

IU – International Unit

94
Q

unit of enzyme activity w/c converts 1 mol of substrate per second

A

Katal

95
Q

conforms w/ the Systemè International (SI) scheme of units

A

Katal

96
Q

Mole is the unit for substrate concentration while the unit of time is second

A

Katal

97
Q

Enzyme concentration is then expressed as

A

katals per liter

98
Q

Factors that influence rate of entry

A
99
Q

Impaired energy production: promote deterioration of cell membrane

A

Leakage of enzymes from cells

100
Q

Direct attack on the cell membranes (viruses or organic chemicals)

A

Leakage of enzymes from cells

101
Q

Reduction in the supply of oxygenated blood perfusing any tissue (e.g. MI)

A

Leakage of enzymes from cells

102
Q

Genetic deficiency of enzyme production

A

Altered enzyme production decrease

103
Q

Enzyme production is depressed as a result of disease

A

Altered enzyme production decrease

104
Q

– NOT a major route for elimination

A

Urinary excretion

105
Q

Except: Amylase = ↑blood levels (e.g. Acute pancreatitis)

A

Urinary excretion

106
Q

Inactivated enzymes are removed by the RES

A

Enzyme Inactivation in Plasma

107
Q

Half – life in plasma: 24 – 48 hours

A

Enzyme Inactivation in Plasma

108
Q

the enzyme changes in shape during binding to accommodate the substrate

A

Induced fit Model

109
Q

The induced-fit model is generally considered the more correct version

A

Induced fit Model

110
Q

This theory maintains that the active site and the substrate are, initially, not perfect matches for each other.

A

Induced fit Model

111
Q

inorganic activators existing as part of the enzyme molecules

A

Metalloenzyme

112
Q

Examples of Inhibitors

A
  1. Excess substrate
  2. Product of reaction
  3. E-S complex does not break to yield products
  4. Chemical substances
113
Q
  • causes competition between substrate molecules for a single binding site
A
  1. Excess substrate
114
Q

-may be an inhibitor of the forward reaction

A
  1. Product of reaction
115
Q

Disruption of the 3-dimensional structure of the enzyme molecule

A

ENZYME DENATURATION

116
Q

ENZYME DENATURATION

• May be reversed if:

A

•denaturation is not extensive
•denaturing agent is removed

117
Q

DENATURING CONDITIONS

A
  1. Elevated temperature
  2. Extremes in pH
  3. Radiation
  4. Frothing
  5. Strong salt solution
  6. Mechanical trauma
  7. Chemicals
118
Q

The (?) is directly proportional to the (?) present in the system

A

rate of an enzyme-catalyzed reaction

amount of active enzyme

119
Q

SOURCES OF ERRORS IN ENZYME ASSAY

A
  1. Use of Plasma
  2. Hemolysis
  3. Turbid/Lactassent Serum (Lipemia)
  4. Heat labile enzyme
  5. Contaminants
120
Q
  • Least preferred specimen
  • inhibitory effects of anticoagulants on enzyme activity
A

Plasma

121
Q

Release of intracellular enzyme

A

Hemolysis

122
Q
  • Inhibits CK & Amylase
A

Turbid/Lactassent Serum (Lipemia)

CC2 LECTURE (33 decks)

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