7) Enzymes Flashcards
(121 cards)
1
Q
3 general properties of enzymes
A
- not altered or consumed during rxn
- reused; only small amounts needed
- accelerate the speed of a rxn without altering equilibrium constant
2
Q
heat-labile protein portion of enzyme
A
apoenzyme
3
Q
a tightly bound coenzyme
A
prosthetic group
4
Q
Apoenzyme and cofactor or coenzyme that form the catalytically active unit
A
holoenzyme
5
Q
Organic or inorganic compounds that are required for enzyme function
A
cofactors
6
Q
Organic cofactors that commonly have a structure related to vitamins
A
coenzymes
7
Q
Enzymes that contain metal ions in their structures
A
metalloenzymes
8
Q
4 types of enzyme specificity
A
- absolute specificity
- group specificity
- bond specificity
- stereospecificity
9
Q
energy of activation
A
Amount of energy required to energize one mole of the substrate to form the activated complex.
10
Q
decreased by enzymes
A
energy of activation
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
12
Q
3 phases of enzyme action
A
- lag phase
- linear phase (zero order)
- substrate depletion phase (first order)
13
Q
explain zero order kinetics
A
Substrate is in excess (rate of enzyme reaction is independent of substrate concentration)
Rx ≠ [S]
14
Q
Amount of product produced per unit of time is constant.
A
linear phase
zero order
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]
16
Q
enzyme activity is measured during…
A
linear phase/zero order kinetics
17
Q
Michaelis-Menten axes
A
velocity of rxn (y-axis)
substrate concentration (x-axis)
18
Q
what is considered a given for each MM curve?
A
enzyme concentration
19
Q
MM equation
A
V = Vmax[S]/Km + [S]
20
Q
——– order kinetics occurs at Vmax
A
zero
21
Q
Km
A
[S] at ½ Vmax
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.
23
Q
—- Km = —- Enzyme affinity
A
↑ Km = ↓ Enzyme affinity
24
Q
double reciprocal plot of MM curve
A
Lineweaver-Burk plot
25
Lineweaver-burk equation
define y, m, x, b
**1/V** = (**Km/Vmax[S]**) + (**1/Vmax**)
y = 1/V
m = Km/Vmax
x = 1/[S]
b = 1/Vmax
26
LB x-int
-1/Km
27
For each ----- increase, the rate of reaction is doubled
10° C
28
Substance is similar to the normal substrate and competes with the substrate for the binding or active site of the enzyme.
competitive inhibition
29
When an inhibitor binds to the E S complex to form an enzyme-substrate inhibiting complex that does not yield product.
uncompetitive inhibition
30
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.
noncompetitive inhibition
31
The addition of more substrate will actually increase the inhibition
uncompetitive
32
Vmax unchanged
Km decreased
LB: same y-int, different slopes
competitive inhibition
33
Vmax decreased
Km unchanged
LB: same x-int, different slopes
noncompetitive inhibition
34
both Vmax and Km decreased
LB: same slopes, different intercepts
uncompetitive inhibition
35
Enzyme measurements are…
Product formation or substrate depletion
36
Multiple forms of an enzyme that can catalyze the reaction
Isoenzymes
37
A cytoplasmic and mitochondrial enzyme that catalyzes the reversible phosphorylation of creatinine by ATP
Creatine kinase
CK
38
CK important to ———— tissue
Muscle
39
CK found in….
Muscle
Brain
Heart
40
3 types of CK
CK-1, or BB—brain and CNS
CK-2, or MB—cardiac muscle
CK-3, or MM—skeletal or cardiac muscle
41
Elevations of C K are found primarily in conditions affecting...
brain
muscle
cardiac muscle
42
most common CK methodology, proceeds faster
reverse (PCr→ Cr)
43
3 methods of measuring CK isoenzymes
immunoinhibition, mass assay, and electrophoresis
44
Sandwich technique is used with two antibodies
One against the M subunit (anti-M)
One against the B subunit (anti-B)
mass assay for CK isoenzyme
45
Can be performed on agarose or cellulose acetate.
CK electrophoresis
46
C K----- migrates most rapidly toward the anode or positive pole.
C K----- migrates midway.
C K----- remains near the point of origin
BB
MB
MM
47
CK relative index
RI = (CKMB/total CK)(100)
| RR: <3%
48
CK index <5%
CK index >5%
crush injury
heart attack/cardiac source
49
A hydrogen transfer enzyme that catalyzes the oxidation of L-lactate to pyruvate with N A D+ as a hydrogen acceptor
lactate dehydrogenase
50
Elevations of ---- without any other information is nonspecific for any disease or disorder.
LD
51
In healthy individuals, the concentration of L D isoenzymes are...
LD-2 > LD-1 > LD-3 > LD-4 > LD-5
52
LD from heart, rbcs, and kidney
LD-1
LD-2
53
LD from spleen, lungs, many tissues
LD-3
54
LD from liver and skeletal muscle
LD-4
LD-5
55
MI effect on LD
LD-1 > LD-2
56
highest levels of LD
pernicious anemia
57
Most current methods measure the interconversion of NAD+ to NADH at 340 nm.
| Wacker procedure
LD methodology
58
Wroblewski and LaDue reverse rxn
LD methodology
59
falsely elevates LD
hemolysis
60
store sample at room temp
LD sample
61
CK peak
CK-MB peak
24 hours
12-20 hours
62
tumor-associated CK
CK-BB
63
3 liver enzymes
Aspartate aminotransferase (AST)
Alanine aminotransferase (ALT)
Alkaline phosphatase (ALP)
64
Marked elevations of ----- and ---- are associated with hepatocellular disease or damage to hepatocytes.
AST
ALT
65
Marked elevation of ---- is associated with hepatobiliary disease or obstructive liver disease.
ALP
66
Catalyzes the interconversion of amino acids and α-oxoacids by the transfer of amino groups
AST
67
Now generally accepted ----- is of little value due to lack of tissue specificity
AST
68
measured using a modification of the Karmen method with the addition of coenzyme P-5-P to ensure full catalytic activity.
AST
69
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Malate dehydrogenase is the indicator reaction measuring the decrease in absorbance at 340 nm as NADH is oxidized to NAD+
AST
70
An aminotransferase that catalyzes the deamination of alanine
ALT
71
highest ALT elevation
acute viral hepatitis
toxic hepatitis
72
**De Ritis Ratio (AST/ALT)**
- alcoholic liver disease, cirrhosis
- Viral hepatitis, acute inflammatory disease and obstructive liver disease
- alcoholism or alcoholic hepatitis
- > 1.0
- < 1.0
- > 2.0
73
Wroblewski and LaDue
Uses lactate dehydrogenase (L D) as the indicator reaction.
ALT methodology
74
Generic name for a group of enzymes with maximum activity in p H range of 9.0 to 10.0.
ALP
75
frees inorganic phosphate from an organic phosphate monoester, resulting in the production of an alcohol at an optimal p H of 10.
ALP
76
ALP richest source
cell membranes of hepatocytes lining the sinusoidal border of the parenchymal cells and the bile canaliculi
osteoblasts in the bone
77
ALP elevations because of osteoblastic activity are associated with ...
Paget’s disease (osteitis deformans)
78
normal ALP elevations
Healing bone fractures (osteoblastic activity)
Pregnancy (placental ALP)
Infants and children (growth spurts)
79
Diet may induce elevations in ALP activity of...
blood group B and O individuals who are secretors
| Values may be 25% higher following ingestion of a high-fat meal
80
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.
ALP methodology
81
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.
Gamma Glutamyl Transferase (GGT)
82
used to evaluate liver function, especially hepatobiliary tract disorders
Most sensitive indicator of alcoholic liver disease
GGT
83
used to differentiate liver disease from bone disease
GGT
| not elevated in bone disease as ALP is
84
Hydrolyzes the phosphate group from nucleoside-5’-phosphates
5’-Nucleotidase (5’-NT, NTP)
85
Useful with A L P and G G T results in determining whether A L P elevation is from bone or liver disease.
5'NT/NTP
86
Predominantly elevated in diseases of the biliary tract where presence of bile salts stimulates its release from hepatocytes.
5'NT/NTP
87
Two most common substrates are:
AMP
Inosine-5’-phosphate (I N P)
5'NT methodology
88
2 pancreatic screening enzymes
Amylase
Lipase
89
A hydrolase that catalyzes the hydrolysis of complex carbohydrates including starch, amylopectin, glycogen, and their partially hydrolyzed products.
Amylase (AMY)
90
increased in acute pancreatitis, obstructive liver disease, acute alcoholism, ectopic pregnancy, and other conditions that affect the pancreas.
AMY
91
acute pancreatitis AMY peak
24 hours
92
non-pancreatic AMY elevation
salivary glands
especially mumps
93
Artifactual increase in serum AMY found in 1% to 2% of the population
Urine AMY?
Macroamylasemia
Urine AMY would be decreased (too big to pass through nephron)
94
Saccharogenic methods
Amyloclastic methods
Chromogenic assay
Enzymatic
Maltotetraose reaction
AMY methodologies
95
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.
acute pancreatitis (>8%)
96
Amylase Creatinine Clearance Ratio (ACCR)
ACCR = (urine AMY)(serum creatinine)/(serum AMY)(urine creatinine)
97
In macroamylasemia, the ACCR is...
<2%
98
Hydrolyzes glycerol esters of long-chain fatty acids (triglycerides) to produce alcohol and fatty acids
lipase (LPS)
99
LPS is less affected by -------------- described under AMY, making it more specific for ------------- but less sensitive.
intraabdominal conditions
acute pancreatitis
100
-------- → Glycerol kinase → L-α-glycerophosphate kinase → Peroxidase
LPS methodology
101
inhibits LPS activity
hemolysis
102
Proteinase that hydrolyzes the peptide bonds formed by the carboxyl groups of lysine or arginine with other amino acids
trypsin (TRY)
103
Important in screening for cystic fibrosis and chronic pancreatitis
TRY
104
Serine proteinase that hydrolyzes peptide bonds connecting the hydroxyl group of tryptophan, leucine, tyrosine, or phenylalanine
chymotrypsin (CHY)
105
used to Investigate chronic pancreatic insufficiency
CHY
106
Enzyme of choice for detecting pancreatic enzymes in the feces
CHY
107
Group of hydrolases similar to alkaline phosphatases
Major difference is the pH of the reaction.
Acid Phosphatase (ACP)
108
tissue richest in ACP
prostate
109
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
ACP
110
unstable at room temperature and requires immediate freezing or buffering
ACP
111
Catalyzes the cleavage of D-fructose-1,6-diphosphate to D-glyceraldehyde-3-phosphate (G L A P) and dihydroxyacetone phosphate (D A P)
aldolase (ALD)
112
Aldolase A is clinically significant for determining the primary pathology between...
muscular versus neurological myopathy
113
ALD main clinical significance
Diagnosing and monitoring skeletal muscle diseases
114
Catalyzes the hydrolysis of choline esters to form choline and the corresponding fatty acid.
| neurotransmitter
Cholinesterase (CHE)
115
2 types of CHE
Acetylcholinesterase (true cholinesterase)
Pseudocholinesterase (acylcholine)
116
Pesticide poisoning
Liver function test
Abnormal genetic variants
CHE
117
Chronic exposure to ---------- by inhalation or through the skin results in a decrease of both acetylcholinesterase and pseudocholinesterase.
organophosphates
118
This enzyme's reaction is the first step in the pentose-phosphate shunt of glucose metabolism and produces NADPH
Glucose-6-Phosphate Dehydrogenase (G6PD)
119
clinically significant because reaction is necessary to make NADPH, required for RBC integrity
G6PD
120
Inherited sex-linked trait (X-chromosome)
administered antimalarial drugs or primaquine
infections
after ingestion of fava beans
G6PD deficiency
121
Seen in heart attacks and megaloblastic anemias
increased G6PD
