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Liz's Clinical Chemistry Module 1 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Define “enzymes”

A

Protein catalysts of biologic origin which enhance the rates of biochemical reactions at a rate as to be compatible with life

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2
Q

What are the 5 general properties of enzymes?

A
  1. Not altered or consumed during the reaction
  2. Only small amounts of enzyme are required
  3. Enzymes accelerate the speed at which a chemical reaction reaches equilibrium, but does not alter the equilibrium constant
  4. Each enzyme is highly specific for a given reaction; they act on only one substrate
  5. Enzymes act by lowering activation energy
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3
Q

Occurs when the 3D structure begins to uncoil

A

Denaturation

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4
Q

High or low (blank) causes denaturation in enzymes

A

Temperature and pH

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5
Q

What is a cofactor?

A

Non-protein compounds required by some enzymes to make them active

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6
Q

What is an inorganic cofactor?

A

Activator

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7
Q

What is an organic cofactor?

A

Coenzyme

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8
Q

Complete cofactor: enzyme complex

A

Holoenzyme

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9
Q

What is a bound cofactor called?

A

Prosthetic group

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10
Q

The protein portion of the enzyme is the ____

A

Apoenzyme

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11
Q

A unique sequence and orientation of amino acids to form a pocket or groove that provides for the enzyme’s specificity for only a unique substrate

A

Active site

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12
Q

A region other than the active site where a separate compound reacts, altering the shape of the active site, altering its fit w/ the substrate; is used to regulate enzyme activity

A

Allosteric site

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13
Q

Different physical forms of an enzyme that all catalyze the same reaction

A

Isoenzymes

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14
Q

The quantity of an enzyme that will catalyze the reaction of one micromole of substrate per minute under defined conditions

A

International unit

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15
Q

Amount of enzyme catalyzed w/ a reaction rate of one mole per second

A

Katal

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16
Q

The rate of enzymatic activity increases as the concentration of substrate increased until the maximum velocity of the reaction is achieved. This max is called the _____?

A

Vmax

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17
Q

Half of the Vmax

A

Km

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18
Q

List examples of activators (inorganic cofactors) and coenzymes (organic cofactors)

A

Inorganic: Zn2+, Fe2+, Cu2+, Mg2+, Mn2+
Organic: NAD+, NADH, NADP+, NADPH, pyrixodal-5-phosphate

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19
Q

Why is enzyme activity, rather than ezyme concentration, measured in the lab?

A

The amount of enzyme is so small, that it’s difficult to devise assays sensitive enough. Instead, the rate of product formed or amount of substrate consumed during reaction is measured. The more enzyme present, the faster the reaction proceeds.

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20
Q

Initial period when enzyme and substrate are first mixed, but no product is formed yet, so there is no detectable change in absorbance

A

Phases of an enzymatic reaction:

lag phase

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21
Q

Rate of product formed is linear w/ time, so reaction follows Beer’s Law

A

Phases of an enzymatic reaction:

log (linear) phase

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22
Q

No change in absorbance b/c there is no substrate left to be converted to product. Rate of reaction is dependent on substrate concentration not enzyme concentration.

A

Phases of enzymatic reaction:

Substrate depletion phase

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23
Q

Why should enzyme measurements be made during the log phase?

A

It corresponds to zero order kinetics! It follows Beers Law so it is an accurate measurement

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24
Q

For a typical enzyme measurement curve, how are the axis labeled?

A

X: time (seconds)
Y: change in absorbance

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25
Q

Enzyme Curve Zero order kinetics

  • Define
  • Where on graph
A
  • The rate of the reaction is independent of reactant (substrate)
  • Corresponds to Log (linear) phase on the graph
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26
Q

Differentiate endpoint and kinetic (multiple point/rate/continuous monitoring) enzyme methods, including why kinetic methods are preferred to endpoint methods for enzyme assays

A

Substrate depletion is observable telling us to dilute the sample

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27
Q

Michaelis-Menten curve:

  • Zero Order kinetics
  • Where on curve
A

At the end of the curve when it starts to flatten out

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28
Q

Michaelis-Menten curve:

  • First Order kinetics
  • Where on curve
A

At the beginning of the curve were it is increasing

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29
Q

Michaelis-Menten curve:

How are the axis labeled?

A

X: [S], concentration of substrate (mol/L)
Y: V, initial reaction rate (mol/Ls)

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30
Q

Michaelis-Menten curve:

Vmax and Km on the curve

A

Vmax: Highest point curve goes
Km: half way up the Vmax

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31
Q

6 factors that influence enzymatic activity

A
  1. enzyme concentration
  2. substrate concentration
  3. temperature
  4. pH
  5. presence of cofactors
  6. presence of inhibitors
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32
Q

Define plasma-specific enzymes

A

Expected to be in higher concentration in blood b/c they function there (i.e., coag factors–fibrinogen, thrombin)

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33
Q

Define non-plasma specific enzymes

A

Have no function in the plasma; function in tissues (cellular metabolism, etc.) (e.g., LD or CK)

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34
Q

Two GENERAL mechanisms for increased enzymes

A
  1. increase in rate of enzyme being released into bloodstream
  2. increase in rate of production of enzyme
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35
Q

7 specific causes of cell damage or death

A
  1. hypoxia
  2. chemicals and drugs
  3. physical agents
  4. microbiological agents
  5. immune mechanisms
  6. genetic defects
  7. nutritional disorders
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36
Q

2 specific causes of increased enzyme production

A
  1. Enzyme induction (via drugs, alcohol, etc)

2. Proliferation of cells that produce that enzyme (cancer)

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37
Q

List 5 physiological factors which affect enzyme reference ranges

A
  1. Sampling time
  2. age
  3. sex
  4. race
  5. exercise (lack of and excessive)
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38
Q

Cholinesterase (ChE)

- In vivo reaction that is catalyzed

A

Hydrolysis of choline esters to form choline and the corresponding fatty acid at the neuromuscular junction

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39
Q

What are the 5 major liver enzymes?

A
  1. aspartate aminotransferase (AST)
  2. alanine aminotransferase (ALT)
  3. Alkaline phosphatase (ALP)
  4. Gamma-glutamyltransferase (GGT)
  5. Cholinesterase (ChE)
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40
Q 
Aspartate Aminotransferase (AST)
- Three biological sources
A
  1. Heart
  2. Skeletal muscle
  3. Liver
    (4. Kidney)
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41
Q 
Aspartate Aminotransferase (AST)
- typical appearance, peak, and return to normal after myocardial infarction
A

Rises w/in 12 hours after onset of chest pain; peaks at 18-24 hours; normal w/in 4-5 days

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42
Q 
Aspartate Aminotransferse (AST)
- Two liver diseases that give rise to the greatest elevations
A

Liver (hepatocellular) Disease

  1. Viral hepatitis
  2. Liver carcinoma
43
Q 
Aspartate Aminotransferase (AST)
- One muscular disease in which AST is elevated
A

Skeletal muscle disease (Muscular Dystrophy)

44
Q 
Aspartate Aminotransferase (AST)
- If hemolyzed specimens are unacceptable
A

UNACCEPTABLE due to high intracellular concentration of AST

45
Q 
Alanine Aminotransferase (ALT)
- principle biological source
46
Q 
Alanine Aminotransferase (ALT)
- Relative use in the dianosis of liver disease, compared to AST
A

Useful in the diagnosis of acute and chronic liver disease; parallels the rise in AST activity

47
Q 
Alanine Aminotransferase (ALT)
- Liver disease in which ALT is elevated
A

Hepatitis; ALT is higher and persists longer than AST

48
Q 
Alanine Aminotransferase (ALT)
- If hemolyzed specimen is unacceptable
A

NO HEMOLYSIS

49
Q 
Alkaline Phosphatase (ALP)
- Four principle biological sources of total ALP
A
  1. Liver
  2. Bone
  3. Intestine
  4. Placenta
50
Q 
Alanine Aminotransferase (ALT)
- Two liver diseases that gives rise to the greatest elevations
A
  1. Hepatitis

2. hepatocellular carcinoma

51
Q 
Alkaline Phosphatase (ALP)
- Hepatobiliary diseases in which ALP is increased
A
  1. Biliary obstruction
  2. Hepatitis
  3. Cirrhosis
  4. Infectious mono
  5. Metastic carcinoma
52
Q 
Alkaline Phosphatase (ALP)
- Hepatobiliary disease which gives rise to ALP's highest elevations
A

Biliary obstruction

53
Q 
Alkaline Phosphatase (ALP)
- Bone diseases in which ALP is increased
A
  1. Bone tumors
  2. Paget’s disease
  3. Rickets
  4. Osteomalacia
  5. Hyperparathyroidism
  6. Healing fractures
54
Q 
Alkaline Phosphatase (ALP)
- Two bone diseases which give rise to ALP's highest elevations
A
  1. Bone tumors

2. Paget’s disease

55
Q 
Alkaline Phosphatase (ALP)
- If hemolyzed specimens are unacceptable
A

Gross hemolysis NOT acceptable (slight is ok, but must be documented)

56
Q 
Alkaline Phosphatase (ALP)
- Principle of the Bowers and McComb procedure using p-Nitrophenylphosphate
A

Reference method; kinetic method that uses pNPP as a substrate and measures the rate of p-Nitrophenoxide release in AMP buffer

57
Q

Which specific isoenzymes may be distinguished using the heat stability, urea denaturation, amino acid inhibition, and electrophoretic techniques?

A

Alkaline Phosphatase (ALP)

58
Q 
Alkaline Phosphatase (ALP)
- Why is the reference range higher in children than in adults?
A

Due to rapid bone growth

59
Q

Gamma-glutamyltransferase (GGT)

- Two principle biological sources

A
  1. Liver mainly

2. Kidney

60
Q

Gamma-glutamyltransferase (GGT)

- clinical usefulness in the diagnosis and monitoring of chronic alcoholism

A

GGT is induced by alcohol and other drugs; used as a marker to check for abstinence from alcohol

61
Q

Cholinesterase (ChE)

- Three clinical applications of measuring decreased ChE activity

A
  1. Assess exposure to organophosphates found in insecticides and nerve gas
  2. Check how patient will react to general anesthesia
  3. Assess presence of cirrhosis, hepatitis, liver carcinoma (due to decreased production)
62
Q

Acetylcholinesterase (AChE)

- Biological sources

A
  1. RBCs

2. CNS

63
Q

Cholinesterase (ChE)

- Biological sources

A
  1. Liver
  2. White matter of brain
  3. Serum
64
Q 
Creatine Kinase (CK)
- In vivo reaction it catalyzes
A

Catalysis for ATP formation and phosphorylation of creatinine in energy production or usage

65
Q 
Creatine Kinase (CK)
- Three principle tissue sources
A
  1. Skeletal muscle
  2. Cardiac muscle
  3. Brain
66
Q 
Creatine Kinase (CK)
- dimeric composition and sources of its three isoenzymes
A

Composed of two subunits (M and B)

Isoenzymes formed: CKMM, CKMB, CKBB

67
Q 
Creatine Kinase (CK)
- Typical appearance, peak, and return to normal after a myocardial infarction
A

Rises 3-8 hours after the onset of chest pain (1st to rise)
Activity peaks at 10-36 hours
Levels return to normal in 3-4 days

68
Q 
Creatine Kinase (CK)
- One muscular disease that gives rise to CK's highest elevations
A

Duchenne’s Muscular Dystrophy (CKMM)

69
Q 
Creatine Kinase (CK)
- Cerebral diseases in which CK is elevated
A

Cerebral vascular accident (CVA), stroke, verebral ischemia (CKBB)

70
Q 
Creatine Kinase (CK)
- Principle of the Oliver and Rosalki method
A

Analytical procedure for total CK; increase in absorbance as NADP+ is oxidized and is measured at 340nm

71
Q 
Creatine Kinase (CK)
- If hemolyzed specimens are acceptable
A

ACCEPTABLE

72
Q 
Lactate Dehydrogenase (LDH)
- In vivo reaction it catalyzes
A

Catalyzes the interconversion of pyruvate and lactate in glycolytic pathway

73
Q 
Lactate Dehydrogenase (LDH)
- Seven principle biological sources
A
  1. Brain
  2. RBCs
  3. WBCs
  4. Kidney
  5. Liver
  6. Lung
  7. Cardiac muscle
  8. Skeletal muscle
74
Q 
Lactate Dehydrogenase (LDH)
- Typical appearance, peak, and return to normal after a myocardial infarction
A

Rises 8-18 hours after onset of chest pain
Peaks ~48-72 hours
Levels return to normal in 6-10 days

75
Q 
Lactate Dehydrogenase (LDH)
- Liver diseases in which LDH is elevated
A
  1. Obstructive jaundice
  2. Cirrhosis
  3. Viral hepatitis
  4. infectious mononucleosis
  5. Toxic jaundice
76
Q 
Lactate Dehydrogenase (LDH)
- Liver disease that gives rise to LDH's highest elevation
A

Hepatobiliary disease (metastatic cancer)

77
Q 
Lactate Dehydrogenase (LDH)
- Two types of anemias in which LDH is elevated
A
  1. Megaloblastic anemia (can’t absorb vitamin B12)

2. Pernicious anemia

78
Q 
Lactate Dehydrogenase (LDH)
- If hemolyzed specimen is unacceptable
A

Acceptable, but make a comment. Hemolysis increases LDH in vivo or in vitro

79
Q

Aldolase (ALS)

- Three principle biological sources

A
  1. Skeletal muscle
  2. Liver
  3. Brain
80
Q

Aldolase (ALS)

- One disease state in which ALS is elevated

A

Muscle dystrophy; can measure along w/ CK, which will also be greatly elevated

81
Q

Amylase (AMS)

- In vivo reaction it catalyzes

A

Breakdown of starch into amylose

82
Q

Amylase (AMS)

- Two principle biological sources

A
  1. Pancreas (40% of total AMS)

2. Salivary glands (60% of total AMS)

83
Q

Amylase (AMS)

-Clinical significance of macroamylase

A

AMS is bound to IgG or IgA, causing an increase in total AMS w/o apparent disease

84
Q

Amylase (AMS)

- Clinical usefulness of AMS measurements in the diagnosis of acute pancreatitis, chronic pancreatitis, and the mumps

A 
Acute pancreatitis
- Increased in serum shortly after onset (may be detectable in urine)
- Peaks w/in 24 hours
- Returns to normal w/in 4 days
Chronic pancreatitis
- ??
Mumps
- AMS is increased
85
Q

Amylase (AMS)

- What method measures amount of sugars formed from hydrolytic activity of AMS

A

Saccharogenic

86
Q

Lipase (LPS)

- Two diseases in which LPS is elevated

A

Acute and chronic pancreatitis

87
Q

Lipase (LPS)

- A comparison b/w the usefulness of LPS and AMS measurements in the diagnosis of pancreatitis

A

Levels parallel AMS appearance, but LPS is more specific than AMS

88
Q

Lipase (LPS)

- Principles of turbidimetric/nephelometric procedures

A

Olive oil emulsion is hydrolyzed by LPS, causing a DECREASE in turbidimetry

89
Q

Lipase (LPS)

- Principle of coupled enzymatic analytical procedure

A

LPS hydrolyzes fatty acids to form free glycerol which is quantitated colorimetrically

90
Q 
Acid Phosphatase (ACP)
- Clinical usefulness of performing ACP measurements
A

Used to diagnose diseases of the prostate; can also do a prostatic acid phosphatase (PAP) and PSA

91
Q

Glucose-6-phosphate dehydrogenase (G-6-PD)

- Biological sources

A

RBCs, adrenal cortex, LN, thymus, spleen

92
Q

Glucose-6-phosphate dehydrogenase (G-6-PD)

-Disease state associated w/ LOW levels of G-6-PD

A

Hemolytic anemia (low levels of NADPH and glutathione which destroys Hgb causing RBCs to lyse)

93
Q

Four major coenzymes used in electron transfer reactions commonly employed in enzyme assays in the lab, including specific wavelength for measurement

A

NAD+, NADH, NADP+, NADPH @ 340nm

94
Q

Clinically significant enzymes/lab findings

- Myocardial infarction

A

Increase in: CKMB, AST, LDH

95
Q

Clinically significant enzymes/lab findings

- Liver (hepatocellular) disease

96
Q

Clinically significant enzymes/lab findings

- Liver (hepatobiliary) disease

97
Q

Clinically significant enzymes/lab findings

- Bone disease

98
Q

Clinically significant enzymes/lab findings

- Brain disease

99
Q

Clinically significant enzymes/lab findings

- Prostate cancer and hypertrophy

100
Q

Clinically significant enzymes/lab findings

- Acute and chronic pancreatitis

101
Q

Clinically significant enzymes/lab findings

- Muscle disease and muscular dystrophy

102
Q

Amylase (AMS)

- What method uses dye-labeled starch substrates; as AMS hydrolyzes the starch, an increase in color is quantified

A

Chromilytic

103
Q

Amylase (AMS)

- What method measures the decrease in starch substrate concentration as AMS works on starch?

A

Amyloclastic assays

104
Q

Amylase (AMS)

- What method consists of a glucose coupled reaction and a hexokinase coupled reaction?

A

Enzymatic assays

Liz's Clinical Chemistry Module 1 (5 decks)

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