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CC2 LECTURE > C1 - Section 3. ENZYMES OF CLINICAL IMPORTANCE > Flashcards

C1 - Section 3. ENZYMES OF CLINICAL IMPORTANCE Flashcards

1
Q

Catalyze interconversions of the amino acids & alpha-ketoacids by transfer of amino groups

A

AMINOTRANSFERASES

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2
Q

as obligate coenzyme

A

Pyridoxal phosphate

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3
Q

will be bound to the apoenzyme and serves as a true prothetic group

A

Pyrodoxal-5’-phosphate

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4
Q

Pyrodoxal-5’-phosphate
will accept the amino group from the first substrates (aspartate/alanine) to form pyridoxamine-5-phosphate and the first product of the reaction –

A

oxaloacetate and pyruvate

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5
Q

the coenzyme in amino form will then transfer the amino group to the acceptor/second substrate (?)-to form the second products of the reaction-p5p is regenerated

A

oxoglutarate

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6
Q

AMINOTRANSFERASES Function:

A

Amino acid metabolism

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7
Q

Ketoacids formed are ultimately oxidized by the

A

TCA Cycle

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8
Q

Formerly SGOT (Serum glutamic-oxalocacetic transaminase)

A

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1

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9
Q

involved in the transfer of an amino group between aspartate and a-keto acids

A

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1

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10
Q

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1
Reaction catalyzed:

A
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11
Q

widely distributed in human tissue

A

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1

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12
Q

Highest concentration: cardiac tissue, liver & skeletal muscle

A

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1

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13
Q

Smaller amounts: kidney, pancreas & RBCs

A

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1

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14
Q

Isoenzymes of AST in the cytoplasm & the mitochondria

A

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1

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15
Q

Both mitochondria and cytoplasmic forms of AST are found in cells.

A

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1

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16
Q

About 5-10% of the AST activity in serum from healthy individuals is of mitochondrial origin

A

ASPARTATE AMINOTRANSFERASE (AST); E.C. 2.6.1.1

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17
Q

Evaluation of hepatocellular disorders & skeletal muscle involvement

A

AST

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18
Q

Liver disease-most important cause of elevated transaminase activity in serum

A

AST

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19
Q

In most liver disease, ALT is higher than AST (Except:?)

A

Alcoholic hepatitis, Hepatic Cirrhosis and liver neoplasia

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20
Q

Mild degree of liver tissue injury: cytoplasmic isoenzyme is predominant

A

AST

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21
Q

Severe tissue damage: release of mitochondrial isoenzyme

A

AST

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22
Q

shows marked increase in patients with extensive liver cell degeneration and damage

A

mitochondrial AST activity in serum

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23
Q

Formerly SGPT (Serum glutamic pyruvic transaminase)

A

ALANINE AMINOTRANSFERASE (ALT); E.C. 2.6.1.2

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24
Q

specifically, catalyze the transfer of an amino group from alanine to a-ketoglutarate with the formation of glutamate and pyruvate

A

ALANINE AMINOTRANSFERASE (ALT); E.C. 2.6.1.2

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25
Q

ALANINE AMINOTRANSFERASE (ALT); E.C. 2.6.1.2
Reaction catalyzed:

A
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26
Q

Distributed in many tissues

A

ALT

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27
Q

High concentrations in the liver (more liver-specific enzyme of the transferases)

A

ALT

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28
Q

low levels in the heart and skeletal muscle

A

ALT

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29
Q

Isoenzyme: exclusively cytoplasmic form

A

ALT

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30
Q

RBC contains 5-8X as much ALT activity as does the serum

A

ALT

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31
Q

Evaluation of hepatic disorders (hepatocellular)

A

ALT

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32
Q

Progressive inflammatory liver conditions: higher ALT elevations than AST

A

ALT

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33
Q

Higher elevations are found in hepatocellular disorders than extrahepatic ot intrahepatic obstructive disorders

A

ALT

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34
Q

diagnostic marker of alcoholic liver disease

A

De Ritis Ratio (AST:ALT ratio)

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35
Q

implication: most causes of liver cell injury, associated w/ greater ALT than AST, however, there are cases where in AST to ALT ratio is 2:1 or greater

A

De Ritis Ratio (AST:ALT ratio)

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36
Q

(also in viral hepatitis)

A

o Normally <1.0

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37
Q

: associated with cirrhosis

A

o If >1.0 but <2.0

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38
Q

: associated with alcoholic hepatitis or hepatocellular carcinoma

A

o If >2.0

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39
Q

: AST>ALT initially; w/in 24-48 hrs., ALT>AST

A

o Acute hepatocellular injury

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40
Q

Higher AST activity in

A

hepatocytes

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41
Q

In (?) of the liver, ALT elevations are frequently higher than those of AST and tend to remain elevated longer as a result of the longer half-life of ALT in serum (16 and 24 hours, respectfully).

A

acute inflammatory conditions

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42
Q

Transaminase reactions coupled to specific dehydrogenase reactions

A

Continuous Monitoring Method

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43
Q

multiple measurement of absorbance change during the reaction is observed

A

Continuous Monitoring Method

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44
Q

The oxo-acids formed in the reaction are measured indirectly by enzymatic reduction to the corresponding hydroxyl acids

A

Continuous Monitoring Method

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45
Q

The accompanying change in NADH concentration is being monitored spectrophotometrically

A

Continuous Monitoring Method

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46
Q

coupled enzymatic reaction w/ MDH (indicator reaction)

A

Assay reaction for AST Activity
Karmen Method

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47
Q

Monitors change in absorbance at 340 nm (NADH to NAD)

A

Assay reaction for AST Activity
Karmen Method

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48
Q

Optimal pH: 7.3 – 7.8

A

Assay reaction for AST Activity
Karmen Method

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49
Q

Hemolysis: increase serum

A

AST

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50
Q

Pyruvate formed is converted to lactate by LDH

A

Assay reaction for ALT Activity

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51
Q

LDH as the indicator enzyme

A

Assay reaction for ALT Activity

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52
Q

NADH formed is oxidized to NAD

A

Assay reaction for ALT Activity

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53
Q

The accompanying change in NADH concentration is being monitored spectrophotometrically

A

Assay reaction for ALT Activity

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54
Q

the disappearance of NADH is followed by measuring he decrease in absorbance

A

Assay reaction for ALT Activity

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55
Q

Change in absorbance is proportional to the micromoles of NADH oxidized that reflects the number of substrate transformed

A

Assay reaction for ALT Activity

56
Q

activity in RBC is 15x higher than in serum

A

AST

57
Q

activity is stable in serum for 3 – 4 days at ref °T

A

AST

58
Q

AST Reference Range:

A

5 – 30 U/L (37°C)

59
Q

Relatively unaffected by hemolysis

A

ALT

60
Q

activity in RBCs is 7x higher than in normal serum)

A

ALT

61
Q

Stable for 3 – 4 days at 4°C

A

ALT

62
Q

ALT Reference Range:

A

6 – 37 U/L (37°C)

63
Q

Coupling w/ 2,4- DNPH (Reitman-Frankel)

A

Colorimetric Method

64
Q

Still feasible

A

Colorimetric Method

65
Q

Phenylhydrazones of oxaloacetate & pyruvate are more chromogenic

A

Colorimetric Method

66
Q

Simple; limited but acceptable accuracy

A

Colorimetric Method

67
Q

Derivative formed will give a strong blue color measured as 505 nm

A

Colorimetric Method

68
Q

An enzyme w/ MW of approximately 82,000

A

Creatine Kinase (E.C. 2.7.3.2)

69
Q

Catalyzes reversible phosphorylation of Creatine by ATP

A

Creatine Kinase (E.C. 2.7.3.2)

70
Q

it is generally associated w/ ATP regeneration in transport system

A

Creatine Kinase (E.C. 2.7.3.2)

71
Q

Its dominant physiologic function is in muscle cells where it is involved in storage of high-energy creatine phosphate (phosphocreatine - major phosphorylated compound in muscle)

A

Creatine Kinase (E.C. 2.7.3.2)

72
Q

CK Reaction catalyzed:

A
73
Q

When muscle contracts, ATP is consumed (to form ADP) & CK catalyzes the rephosphorylation of ADP to form ATP, using Phosphocreatine

A

Creatine Kinase (E.C. 2.7.3.2)

74
Q

Mg-forms complexes with ATP and ADP with narrow concentration because excess will be inhibitory

A

Creatine Kinase (E.C. 2.7.3.2)

75
Q

Greatest in striated muscle, brain tissue & heart tissue

A

CK

76
Q

Smaller quantities: bladder, placenta, GIT, Thyroid, uterus, kidney, lung, prostate, spleen & pancreas

A

CK

77
Q

liver and erythrocyte is devoid of the activity of CK

A

CK

78
Q

Dimer w/ 2 sub-units: B (brain) & M (muscle)

A

CK

79
Q

Each sub-unit w/ a MW of ~ 40,000

A

CK

80
Q

CK Three major isoenzymes:

A
81
Q

 Found in the brain, prostate, gut, lung, bladder, uterus, placenta & thyroid

A

CK – BB (brain type) CK1

82
Q

 present in varying degrees in heart muscle (25 – 46% of CK activity) and minor degree in skeletal muscle

A

CK – MB (hybrid type) CK2

83
Q

 predominates in skeletal & cardiac muscle

A

CK – MM (muscle type) CK3

84
Q

All three CK isoenzymes are found in the

A

cell cytosol

85
Q

Unusual CK isoenzymes

A
86
Q

migrates cathodic of CK-MM

A

CK-Mt : 4th isoenzyme

87
Q

Located b/w the inner & outer membranes of the mitochondria

A

CK-Mt : 4th isoenzyme

88
Q

Differs immunologically & in electrophoretic mobility

A

CK-Mt : 4th isoenzyme

89
Q

Constitutes up to 15% CK activity in the heart

A

CK-Mt : 4th isoenzyme

90
Q

Its presence does not correlate with any specific disease however it correlates with severe illness and cases of malignant tumor and cardiac abnormality

A

CK-Mt : 4th isoenzyme

91
Q

CK1 associated with IgG or CK3 w/ IgA

A

Macro CK Type 1

92
Q

Oligomeric CK-Mt

A

Macro CK Type 2

93
Q

All types of muscular dystrophy, esp. Duchenne type sex-linked progressive muscular dystrophy)

A

Disease of the Skeletal Muscle

94
Q

which may show up to 50x the ULN

A

Disease of the Skeletal Muscle

95
Q

Normal Serum CK activity is seen in

A

Neurogenic muscle disease

96
Q

CKMM major CK in serum of healthy people where Skeletal muscle contains almost exclusively of CKMM and heart muscle activity is attributed to CKMM

A

Disease of the Skeletal Muscle

97
Q

Injury on both heart and skeletal will mean elevation of CKMM

A

Disease of the Skeletal Muscle

98
Q

CK level: sensitive indicator of AMI (Total CK & CK-2)

A

Disease of the Heart

99
Q

CK-MB levels begin to rise w/in 4 – 8 hrs. Peak at 12 – 24 hrs. & return to normal levels w/in 48 – 72 hrs.

A

Disease of the Heart

100
Q

Elevation of Total CK: Cardiac trauma ff. heart surgery (including transplantation)

A

Disease of the Heart

101
Q

CKMB activity has been observed in other cardiac conditions, not entirely specific for AMI although specificity can increase if tested in conjunction with LDH

A

Disease of the Heart

102
Q

The time course of CK is unique in AMI

A

Disease of the Heart

103
Q

isoenzyme will be elevated in conditions such as cerebral ischemia and cerebrovascular ischemia where blood flow to the brain is insufficient

A

CKBB

104
Q

Elevations are also noted during head injury and acute cerebrovascular disease

A

Disease of the CNS

105
Q

It is also observe that the activity may increase in conditions that affects children such as Reye’s syndrome where the liver and the brain is swollen as a side effect of viral infections

A

CK BB

106
Q

60% of hypothyroid subjects

A

Disease of the Thyroid

107
Q

Major isoenzyme is CK-3

A

Disease of the Thyroid

108
Q

Hypothyroidism results in (?) elevations because of the involvement

A

CK-MM

109
Q

of muscle tissue (increased membrane permeability), the effect of thyroid hormone on enzyme activity, and, possibly, the slower clearance of CK as a result of slower metabolism.

A

CK MM

110
Q

is rarely seen in the serum bec. Of its molecular size

A

CKBB

111
Q

Extensive damage to the brain may lead to the leakage of it in the serum

A

CK activity in Malignancy

112
Q

is associated also with patients with carcinoma of various organs such as adenocarcinoma, lung tumors, tumors of the prostate, kidney breasts and ovary the

A

CKBB

113
Q

CKBB can be a useful tumor marker

A

CK activity in Malignancy

114
Q

Makes use of coupled enzymatic reaction, either the forward or reverse reaction

A

CK

115
Q

is set at a pH of 9.0 and the reduction of NADH to NAD is monitored spectrophotometrically

A

The forward reaction

116
Q

is proportional to the activity of CK

A

The change in absorbance

117
Q

– an enzyme released from erythrocytes in hemolyzed samples and appearing as a band cathodal to CK-MM.

A

Adenylate kinase (AK) Effect

118
Q

may interfere with chemical or immunoinhibition methods, causing a falsely elevated CK or CK-MB value

A

Adenylate kinase (AK) Effect

119
Q

reacts w/ ADP to produce ATP

A
120
Q

causes falsely elevated CK activity

A
121
Q

Hemolysis – RBCs are devoid of (?) but are rich in AK, thus hemolysis should be avoided

A

CK

122
Q

Reference range
 TOTAL CK:
Male :
Female :
 CK – MB :

A

 TOTAL CK:
Male : 15 – 160 U/L (37°C)
Female : 15 – 130 U/L (37°C)
 CK – MB : < 6% Total CK

123
Q

Separation Techniques

A
124
Q

– reference method and the most useful method

A

Electrophoresis

125
Q

bands are visualized by incubating the support with a concentrated CK assay using the reverse reaction

A

Electrophoresis

126
Q

NADPH formed is observed with the bluish-white fluorescence after excitation by ultra violet light

A

Electrophoresis

127
Q

Allows visualization of AK

A

Electrophoresis

128
Q

Potential for being more sensitive & precise than electrophoresis

A
129
Q

On unsatisfactory column:
may merge into CK-MB
may be eluted w/ CK-MB
may elute w/ CK-MB

A

CK-MM

CK-BB

Macro-CK

130
Q

Measure the conc. of Enzyme protein rather than Enzyme activity

A

Immunoassays

131
Q

detects enzymatically inactive CK-2

A

Immunoassays

132
Q

an anti-CK-M subunit antiserum is used to inhibit both M subunits of CK-MM and the single M subunit og CK-MB and allows determination of the enzyme activity of the B subunit of CK-MB and the B subunit of CK-BB

A

Immunoinhibition

133
Q

The residual activity after inhibition is multiplied by 2 to account for MB activity (50% inhibited). The major disadvantage of this method is that it detects BB activity, which, although not normally detectable, will cause falsely elevated MB results when BB is present.

A

Immunoinhibition

134
Q

In addition, the atypical forms of CK-Mi and macro-CK are not inhibited by anti-M antibodies and also may cause erroneous results for MB activity.

A

Immunoinhibition

135
Q

catalyzes the interconversion of lactic acid and pyruvic acids  NAD - a hydrogen transfer enzyme that uses the coenzyme NAD as a hydrogen acceptor  Reaction catalyzed:

A

CC2 LECTURE (33 decks)

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