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Mercy CLS 5: Chemistry > 7) Enzymes > Flashcards

7) Enzymes Flashcards

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1
Q

3 general properties of enzymes

A
  1. not altered or consumed during rxn
  2. reused; only small amounts needed
  3. accelerate the speed of a rxn without altering equilibrium constant
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2
Q

heat-labile protein portion of enzyme

A

apoenzyme

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3
Q

a tightly bound coenzyme

A

prosthetic group

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4
Q

Apoenzyme and cofactor or coenzyme that form the catalytically active unit

A

holoenzyme

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5
Q

Organic or inorganic compounds that are required for enzyme function

A

cofactors

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6
Q

Organic cofactors that commonly have a structure related to vitamins

A

coenzymes

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7
Q

Enzymes that contain metal ions in their structures

A

metalloenzymes

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8
Q

4 types of enzyme specificity

A
  1. absolute specificity
  2. group specificity
  3. bond specificity
  4. stereospecificity
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9
Q

energy of activation

A

Amount of energy required to energize one mole of the substrate to form the activated complex.

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10
Q

decreased by enzymes

A

energy of activation

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11
Q

1 IU/L

A

Amount of enzyme that produces 1 𝜇mol of product per minute under standardized conditions of temperature, pH, substrate, and activators

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12
Q

3 phases of enzyme action

A
  1. lag phase
  2. linear phase (zero order)
  3. substrate depletion phase (first order)
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13
Q

explain zero order kinetics

A

Substrate is in excess (rate of enzyme reaction is independent of substrate concentration)

Rx ≠ [S]

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14
Q

Amount of product produced per unit of time is constant.

A

linear phase
zero order

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15
Q

explain first order kinetics

A

The velocity is directly proportional to the substrate concentration. Period of reduced velocity as substrate no longer in excess.

Rx = [S]

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16
Q

enzyme activity is measured during…

A

linear phase/zero order kinetics

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17
Q

Michaelis-Menten axes

A

velocity of rxn (y-axis)
substrate concentration (x-axis)

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18
Q

what is considered a given for each MM curve?

A

enzyme concentration

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19
Q

MM equation

A

V = Vmax[S]/Km + [S]

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20
Q

——– order kinetics occurs at Vmax

A

zero

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21
Q

Km

A

[S] at ½ Vmax

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22
Q

Vmax

A

When the substrate concentration is high enough that all enzyme molecules are bound to the substrate and all active sites are engaged.

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23
Q

—- Km = —- Enzyme affinity

A

↑ Km = ↓ Enzyme affinity

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24
Q

double reciprocal plot of MM curve

A

Lineweaver-Burk plot

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25
Q

Lineweaver-burk equation
define y, m, x, b

A

1/V = (Km/Vmax[S]) + (1/Vmax)

y = 1/V
m = Km/Vmax
x = 1/[S]
b = 1/Vmax

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26
Q

LB x-int

A

-1/Km

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27
Q

For each —– increase, the rate of reaction is doubled

A

10° C

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28
Q

Substance is similar to the normal substrate and competes with the substrate for the binding or active site of the enzyme.

A

competitive inhibition

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29
Q

When an inhibitor binds to the E S complex to form an enzyme-substrate inhibiting complex that does not yield product.

A

uncompetitive inhibition

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30
Q

Inhibitor is structurally different than the substrate and binds to an allosteric site on the enzyme molecule, which is far removed from the active site.

A

noncompetitive inhibition

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31
Q

The addition of more substrate will actually increase the inhibition

A

uncompetitive

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32
Q

Vmax unchanged
Km decreased

LB: same y-int, different slopes

A

competitive inhibition

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33
Q

Vmax decreased
Km unchanged

LB: same x-int, different slopes

A

noncompetitive inhibition

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34
Q

both Vmax and Km decreased

LB: same slopes, different intercepts

A

uncompetitive inhibition

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35
Q

Enzyme measurements are…

A

Product formation or substrate depletion

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36
Q

Multiple forms of an enzyme that can catalyze the reaction

A

Isoenzymes

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37
Q

A cytoplasmic and mitochondrial enzyme that catalyzes the reversible phosphorylation of creatinine by ATP

A

Creatine kinase
CK

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38
Q

CK important to ———— tissue

A

Muscle

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39
Q

CK found in….

A

Muscle
Brain
Heart

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40
Q

3 types of CK

A

CK-1, or BB—brain and CNS
CK-2, or MB—cardiac muscle
CK-3, or MM—skeletal or cardiac muscle

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41
Q

Elevations of C K are found primarily in conditions affecting…

A

brain
muscle
cardiac muscle

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42
Q

most common CK methodology, proceeds faster

A

reverse (PCr→ Cr)

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43
Q

3 methods of measuring CK isoenzymes

A

immunoinhibition, mass assay, and electrophoresis

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44
Q

Sandwich technique is used with two antibodies
One against the M subunit (anti-M)
One against the B subunit (anti-B)

A

mass assay for CK isoenzyme

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45
Q

Can be performed on agarose or cellulose acetate.

A

CK electrophoresis

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46
Q

C K—– migrates most rapidly toward the anode or positive pole.
C K—– migrates midway.
C K—– remains near the point of origin

A

BB
MB
MM

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47
Q

CK relative index

A

RI = (CKMB/total CK)(100)

RR: <3%

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48
Q

CK index <5%
CK index >5%

A

crush injury
heart attack/cardiac source

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49
Q

A hydrogen transfer enzyme that catalyzes the oxidation of L-lactate to pyruvate with N A D+ as a hydrogen acceptor

A

lactate dehydrogenase

50
Q

Elevations of —- without any other information is nonspecific for any disease or disorder.

A

LD

51
Q

In healthy individuals, the concentration of L D isoenzymes are…

A

LD-2 > LD-1 > LD-3 > LD-4 > LD-5

52
Q

LD from heart, rbcs, and kidney

A

LD-1
LD-2

53
Q

LD from spleen, lungs, many tissues

A

LD-3

54
Q

LD from liver and skeletal muscle

A

LD-4
LD-5

55
Q

MI effect on LD

A

LD-1 > LD-2

56
Q

highest levels of LD

A

pernicious anemia

57
Q

Most current methods measure the interconversion of NAD+ to NADH at 340 nm.

Wacker procedure

A

LD methodology

58
Q

Wroblewski and LaDue reverse rxn

A

LD methodology

59
Q

falsely elevates LD

A

hemolysis

60
Q

store sample at room temp

A

LD sample

61
Q

CK peak
CK-MB peak

A

24 hours
12-20 hours

62
Q

tumor-associated CK

A

CK-BB

63
Q

3 liver enzymes

A

Aspartate aminotransferase (AST)
Alanine aminotransferase (ALT)
Alkaline phosphatase (ALP)

64
Q

Marked elevations of —– and —- are associated with hepatocellular disease or damage to hepatocytes.

A

AST
ALT

65
Q

Marked elevation of —- is associated with hepatobiliary disease or obstructive liver disease.

A

ALP

66
Q

Catalyzes the interconversion of amino acids and α-oxoacids by the transfer of amino groups

A

AST

67
Q

Now generally accepted —– is of little value due to lack of tissue specificity

A

AST

68
Q

measured using a modification of the Karmen method with the addition of coenzyme P-5-P to ensure full catalytic activity.

A

AST

69
Q

Malate dehydrogenase is the indicator reaction measuring the decrease in absorbance at 340 nm as NADH is oxidized to NAD+

A

AST

70
Q

An aminotransferase that catalyzes the deamination of alanine

A

ALT

71
Q

highest ALT elevation

A

acute viral hepatitis
toxic hepatitis

72
Q

De Ritis Ratio (AST/ALT)
- alcoholic liver disease, cirrhosis
- Viral hepatitis, acute inflammatory disease and obstructive liver disease
- alcoholism or alcoholic hepatitis

A
  • > 1.0
  • < 1.0
  • > 2.0
73
Q

Wroblewski and LaDue
Uses lactate dehydrogenase (L D) as the indicator reaction.

A

ALT methodology

74
Q

Generic name for a group of enzymes with maximum activity in p H range of 9.0 to 10.0.

A

ALP

75
Q

frees inorganic phosphate from an organic phosphate monoester, resulting in the production of an alcohol at an optimal p H of 10.

A

ALP

76
Q

ALP richest source

A

cell membranes of hepatocytes lining the sinusoidal border of the parenchymal cells and the bile canaliculi

osteoblasts in the bone

77
Q

ALP elevations because of osteoblastic activity are associated with …

A

Paget’s disease (osteitis deformans)

78
Q

normal ALP elevations

A

Healing bone fractures (osteoblastic activity)
Pregnancy (placental ALP)
Infants and children (growth spurts)

79
Q

Diet may induce elevations in ALP activity of…

A

blood group B and O individuals who are secretors

Values may be 25% higher following ingestion of a high-fat meal

80
Q

Bowers and McComb procedure

4-nitrophenol phosphate (4-N P P) [formerly Ρ-nitrophenylphosphate (Ρ-N P P)] is the substrate, and the yellow product, 4-nitrophenoxide, is measured at 405 nm.

A

ALP methodology

81
Q

Transfers the γ-glutamyl group from glutathione and other γ-glutamyl peptides to amino acids or small peptides to form the γ amino acids and cysteinyl-glycine.

A

Gamma Glutamyl Transferase (GGT)

82
Q

used to evaluate liver function, especially hepatobiliary tract disorders

Most sensitive indicator of alcoholic liver disease

A

GGT

83
Q

used to differentiate liver disease from bone disease

A

GGT

not elevated in bone disease as ALP is

84
Q

Hydrolyzes the phosphate group from nucleoside-5’-phosphates

A

5’-Nucleotidase (5’-NT, NTP)

85
Q

Useful with A L P and G G T results in determining whether A L P elevation is from bone or liver disease.

A

5’NT/NTP

86
Q

Predominantly elevated in diseases of the biliary tract where presence of bile salts stimulates its release from hepatocytes.

A

5’NT/NTP

87
Q

Two most common substrates are:
AMP
Inosine-5’-phosphate (I N P)

A

5’NT methodology

88
Q

2 pancreatic screening enzymes

A

Amylase
Lipase

89
Q

A hydrolase that catalyzes the hydrolysis of complex carbohydrates including starch, amylopectin, glycogen, and their partially hydrolyzed products.

A

Amylase (AMY)

90
Q

increased in acute pancreatitis, obstructive liver disease, acute alcoholism, ectopic pregnancy, and other conditions that affect the pancreas.

A

AMY

91
Q

acute pancreatitis AMY peak

A

24 hours

92
Q

non-pancreatic AMY elevation

A

salivary glands

especially mumps

93
Q

Artifactual increase in serum AMY found in 1% to 2% of the population

Urine AMY?

A

Macroamylasemia

Urine AMY would be decreased (too big to pass through nephron)

94
Q

Saccharogenic methods
Amyloclastic methods
Chromogenic assay
Enzymatic
Maltotetraose reaction

A

AMY methodologies

95
Q

ACCR is elevated in …….., because the renal clearance of AMY is greater than that of CR, but returns to normal levels after the AMY is cleared from the serum.

A

acute pancreatitis (>8%)

96
Q

Amylase Creatinine Clearance Ratio (ACCR)

A

ACCR = (urine AMY)(serum creatinine)/(serum AMY)(urine creatinine)

97
Q

In macroamylasemia, the ACCR is…

A

<2%

98
Q

Hydrolyzes glycerol esters of long-chain fatty acids (triglycerides) to produce alcohol and fatty acids

A

lipase (LPS)

99
Q

LPS is less affected by ————– described under AMY, making it more specific for ————- but less sensitive.

A

intraabdominal conditions
acute pancreatitis

100
Q

——– → Glycerol kinase → L-α-glycerophosphate kinase → Peroxidase

A

LPS methodology

101
Q

inhibits LPS activity

A

hemolysis

102
Q

Proteinase that hydrolyzes the peptide bonds formed by the carboxyl groups of lysine or arginine with other amino acids

A

trypsin (TRY)

103
Q

Important in screening for cystic fibrosis and chronic pancreatitis

A

TRY

104
Q

Serine proteinase that hydrolyzes peptide bonds connecting the hydroxyl group of tryptophan, leucine, tyrosine, or phenylalanine

A

chymotrypsin (CHY)

105
Q

used to Investigate chronic pancreatic insufficiency

A

CHY

106
Q

Enzyme of choice for detecting pancreatic enzymes in the feces

A

CHY

107
Q

Group of hydrolases similar to alkaline phosphatases

Major difference is the pH of the reaction.

A

Acid Phosphatase (ACP)

108
Q

tissue richest in ACP

A

prostate

109
Q

Benign prostate hypertrophy (BPH) and prostate surgery.

Was also used in forensics in the investigation of rape

Bone disease is a third category of elevation

A

ACP

110
Q

unstable at room temperature and requires immediate freezing or buffering

A

ACP

111
Q

Catalyzes the cleavage of D-fructose-1,6-diphosphate to D-glyceraldehyde-3-phosphate (G L A P) and dihydroxyacetone phosphate (D A P)

A

aldolase (ALD)

112
Q

Aldolase A is clinically significant for determining the primary pathology between…

A

muscular versus neurological myopathy

113
Q

ALD main clinical significance

A

Diagnosing and monitoring skeletal muscle diseases

114
Q

Catalyzes the hydrolysis of choline esters to form choline and the corresponding fatty acid.

neurotransmitter

A

Cholinesterase (CHE)

115
Q

2 types of CHE

A

Acetylcholinesterase (true cholinesterase)
Pseudocholinesterase (acylcholine)

116
Q

Pesticide poisoning
Liver function test
Abnormal genetic variants

A

CHE

117
Q

Chronic exposure to ———- by inhalation or through the skin results in a decrease of both acetylcholinesterase and pseudocholinesterase.

A

organophosphates

118
Q

This enzyme’s reaction is the first step in the pentose-phosphate shunt of glucose metabolism and produces NADPH

A

Glucose-6-Phosphate Dehydrogenase (G6PD)

119
Q

clinically significant because reaction is necessary to make NADPH, required for RBC integrity

A

G6PD

120
Q

Inherited sex-linked trait (X-chromosome)

administered antimalarial drugs or primaquine
infections
after ingestion of fava beans

A

G6PD deficiency

121
Q

Seen in heart attacks and megaloblastic anemias

A

increased G6PD

Mercy CLS 5: Chemistry (24 decks)

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