Clinical Enzymology Flashcards
muscles, pancreatic, livers and malignancy enzymes (153 cards)
1
Q
mention the muscle enzymes
A
Creatine kinase
Aldolase
Glycogen phosphorylase
2
Q
What is the function of creatine kinase (CK)?
A
CK catalyzes the reversible phosphorylation of creatine (Cr) by ATP.
3
Q
What are the subunits of CK?
A
The subunits are B and M
4
Q
Name the three different possible pairs of CK subunits.
A
BB (CK-1), MB (CK-2), MM (CK-3)
5
Q
How does CK contribute to energy supply during muscle contraction?
A
When muscles contract, ATP is converted to ADP, and CK rephosphorylates ADP to ATP using creatine phosphate as a phosphorylation reservoir.
6
Q
Write down the chemical reactions for the reversible phosphorylation at pH 9.0 and 6.7, respectively.
A
At pH 9.0: Cr + ATP → ADP + CrP
At pH 6.7: CrP + ADP → ATP + Cr
7
Q
Which ion is an obligate activating ion for CK
A
Mg^(2+) ion
8
Q
List some metal ions that inhibit CK enzyme activity.
A
Mn^(2+), Ca^(2+), Zn^(2+), and Cu^(2+).
9
Q
What other substances can inhibit CK activity?
A
Excess ADP, citrate, fluoride, nitrate, acetate, iodide, bromide, malonate, urate, and cystine.
10
Q
Why is CK considered unstable?
A
CK is unstable due to sulfhydryl group oxidation
11
Q
In which tissues is CK activity high
A
CK activity is high in striated muscle, heart tissue, the gastrointestinal tract, and the urinary bladder
12
Q
Which parts of the body are essentially devoid of CK activity
A
The liver and erythrocytes.
13
Q
How does Mg^2+ contribute to the CK reaction?
A
Mg^2+ forms complexes with ATP and ADP, acting as an obligate activating ion
14
Q
explain 4 clinical significances of creatine kinase
A
- Serum CK activity is increased in all patients with injury, inflammation, necrosis(death of cells within an orgsn) of skeletal or heart tissue
- Elevation of CK activity can be the only sign of clinical neuromascular disorders including progressive muscular dystrophy
- Increased CK activity may also be present in viral myositis (inflammation of the muscles that are used to move the body), polymyositis
- Serum CK iso enzyme have been used to diagnose myocardial infarction
15
Q
what are the reference ranges/intervals for creatine kinase
A
- males: 46 - 171 U/L
- females: 34 - 145
16
Q
What methods are used for creatine kinase determination
A
Creatine kinase (CK) determination involves spectrophotometric monitoring of the conversion of NADP^+ to NADPH at 340 nm.
17
Q
How is NADPH monitored in the process of creatine kinase determination?
A
NADPH production during the CK reaction is monitored using spectrophotometry at a wavelength of 340 nm.
18
Q
What role does N-acetylcysteine play in optimizing the CK determination reaction?
A
N-acetylcysteine activates CK and optimizes the reaction.
19
Q
Why is EDTA added to the reaction mixture during CK determination?
A
EDTA binds Ca^(2+) ions, stabilizing the reaction mixture and enhancing CK determination
20
Q
How does Adenosine pentaphosphate (Ap5A) and AMP affect adenylate kinase during CK determination?
A
Ap5A and AMP inhibit adenylate kinase (AK), preventing interference in CK measurement.
21
Q
Which specimens are suitable for CK analysis and why
A
Serum and plasma from heparinized tubes are suitable because other anticoagulants inhibit CK activity.
22
Q
How does an anticoagulant other than heparin affect CK activity
A
Anticoagulants other than heparin reduce CK activity.
23
Q
Does moderate hemolysis affect CK activity? Explain
A
No, moderate hemolysis does not significantly affect CK activity because red blood cells (RBCs) contain no CK.
24
Q
How long can CK be stabilized at room temperature, 4°C, and −20°C respectively?
A
Room temperature: Stabilized for 8 hours
4°C: Stabilized for 48 hours
−20°C: Stabilized for 1 month
25
Explain why RBCs do not significantly affect CK activity
RBCs lack CK activity, so their presence does not interfere with CK measurement.
26
27
What methods are used to separate CK isoenzymes?
Electrophoretic methods are used for the separation of CK isoenzymes
28
How are the isoenzyme bands visualized during the separation process?
The isoenzyme bands are visualized by incubating the support media with a concentrated CK assay mixture using the reverse reaction
29
What is detected by observing bluish-white fluorescence after excitation at 360 nm ultraviolet light?
NADPH formed in this reaction is detected by observing bluish-white fluorescence after excitation at 360 nm ultraviolet light
30
How do CK isoenzymes migrate at pH 8.6, and what is their order of migration toward the anode?
At pH 8.6, CK isoenzymes migrate toward the anode in the order of BB > MB > MM.
31
Describe how concentrations of the CK-MB protein are commonly measured.
Immunoassays with monoclonal antibodies.
32
What recognizes CK-MB dimers during immunoassays
CK-MB dimers are recognized by a monoclonal antibody.
33
Compare the sensitivity of mass assay and activity-based methods in measuring concentrations of CK-MB protein.
Mass assay is more sensitive than the activity-based method and is less affected by hemolysis and anticoagulants.
34
What is ALD, and what is its function in the glycolytic breakdown of glucose?
ALD is a tetramer enzyme.
It catalyzes the splitting of D-fructose-1,6-diphosphate into two molecules: D-glyceraldehyde-3-phosphate (GLAP) and dihydroxyacetone-phosphate (DHAP)
35
Describe the process by which ALD facilitates the splitting of D-fructose-1,6-diphosphate.
1. ALD acts as a catalyst in this reaction.
2. It cleaves the D-fructose-1,6-diphosphate substrate into GLAP and DHAP
36
What are GLAP and DHAP, and how are they related to the function of ALD
1. GLAP (D-glyceraldehyde-3-phosphate) and DHAP (dihydroxyacetone-phosphate) are the products of ALD’s enzymatic activity.
2. They play a crucial role in the glycolytic pathway, where glucose is broken down to lactate.
37
Explain the role of ALD in converting glucose to lactate
ALD’s action is part of the glycolysis pathway, which ultimately leads to the production of lactate from glucose.
38
What is the clinical significance of increased ALD activity in neuromuscular diseases
Increased ALD activity is useful in distinguishing neuromuscular atrophies from myopathies when combined with the CK/AST ratio.
39
How does the CK/AST ratio complement increased ALD activity in diagnosing muscle diseases?
The CK/AST ratio helps to differentiate between neuromuscular atrophies and myopathies, providing a more comprehensive diagnosis when considered alongside ALD activity.
40
Is ALD activity alone sufficient for diagnosing suspected muscle disease?
No, ALD activity in serum of subjects with suspected muscle disease does not add information that isn’t more readily available from measurement of other enzymes, especially CK
41
Which enzyme is particularly significant in providing information about suspected muscle disease?
Creatine kinase (CK) provides more readily available information for diagnosing suspected muscle disease than ALD activity
42
What role does the measurement of other enzymes play in understanding and diagnosing suspected muscle diseases compared to just focusing on ALD activity?
Measurement of other enzymes, especially CK, offers more readily available and comprehensive information necessary for accurate diagnosis and understanding of suspected muscle diseases.
43
Why isn’t increased ALD activity typically used as a standalone indicator for muscle diseases?
Because it doesn’t provide additional information beyond what can be obtained from other enzymes, especially CK, making it not as efficient for diagnosis on its own.
44
what are the reference intervals for ALD
In aldults it is 2.5 to 10 U/L at 37 degree celcius
45
What is the role of Triosephosphate isomerase in the ALD assay?
Triosephosphate isomerase ensures the rapid conversion of all DAP (dihydroxyacetone-phosphate) to GLAP (glyceraldehyde-3-phosphate).
46
How is GLAP converted to glycerol-3-phosphate?
Glycerol-3-phosphate dehydrogenase is added to reduce GLAP to glycerol-3-phosphate
47
What acts as a hydrogen donor in the reduction of GLAP to glycerol-3-phosphate?
NADH (nicotinamide adenine dinucleotide) acts as the hydrogen donor in this enzymatic reaction.
48
How is the decrease in NADH concentration measured
The decrease in NADH concentration is measured at 340nm using spectrophotometry.
49
what is the difference between thebetween ALD activity between adults and children
In children, ALD activity is twice that in the adult and adult values are attained by the time the child reaches puberty
50
What is the role of glycogen phosphorylase in carbohydrate metabolism?
Glycogen phosphorylase plays an essential role in regulating carbohydrate metabolism by mobilizing glycogen.
51
What is the first step catalyzed by glycogen phosphorylase in glycogenolysis?
Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate during glycogenolysis
52
What is the physiologic role of muscle GP
The physiologic role of muscle GP is to provide fuel for the energy supply required for muscle contraction.
53
What is the role of glycogen phosphorylase in carbohydrate metabolism
Glycogen phosphorylase plays an essential role in regulating carbohydrate metabolism by mobilizing glycogen.
54
What are the three isoenzymes of glycogen phosphorylase, and where are they predominantly found?
GP-LL: Predominant in all tissues except heart, skeletal muscle, and brain.
GP-MM: Found only in adult skeletal muscle.
GP-BB: Predominant in the brain.
55
Why is GP-MM particularly significant in adult skeletal muscle?
GP-MM is the primary isoenzyme in adult skeletal muscle, responsible for glycogenolysis and providing glucose for energy during muscle contraction.
56
what is the clinical significance of glycogen phosphorylase
test for the diagnosis of myocardial infarction
57
methods fro measurement of glycogen phosphorylase
1. Manual ELISA assays are employed for the determination of isoenzyme GP-BB.
2. The calculated upper reference limit is 10 μg/L
58
mentions 2 pancreatic enzymes
1. Lipase
2. Amylases
59
What does lipase (LPS) hydrolyze?
LPS hydrolyzes glycerol esters of long chain fatty acids
60
How much greater is the concentration of LPS in the pancreas compared to other tissues?
The concentration of LPS in the pancreas is approximately 5000-fold greater than in other tissues.
61
What is required for LPS activity and specificity
LPS activity requires the presence of bile salts and a cofactor called colipase.
62
Where is LPS activity found in serum primarily derived from?
LPS activity found in serum is primarily derived from the pancreas.
63
Besides the pancreas, where else is LPS secreted?
LPS is also secreted by gastric, pulmonary, and intestinal mucosa.
64
Can the kidney filter LPS, and what happens afterward
Yes, the kidney can filter LPS, but it is totally reabsorbed afterward.
65
What role does colipase play in the activity of lipase?
Colipase is a cofactor that enhances the specificity and efficiency of lipase activity
66
What is the typical timeline of increased LPS activity in acute pancreatitis?
LPS activity increases within 4 to 8 hours, peaks at 24 hours, and then decreases within 8 to 14 days during acute pancreatitis.
67
Is the increase in serum LPS activity always proportional to the severity of an acute pancreatitis attack? Explain
: No, the increase in serum LPS activity is not necessarily proportional to the severity of the attack.
68
How does a reduced glomerular filtration rate affect serum LPS activity?
In patients with a reduced glomerular filtration rate, serum LPS activity is increased.
69
In addition to acute pancreatitis, in which other conditions does LPS activity elevate
LPS activity also elevates in penetrating duodenal ulcers, perforated peptic ulcers, intestinal obstruction, and acute cholecystitis
70
What is the significance of increased lipase in acute pancreatitis?
Increased lipase levels are a significant indicator of acute pancreatitis. Lipase is an enzyme produced by the pancreas that helps break down fats in the intestines. In acute pancreatitis, the pancreas becomes inflamed, and lipase leaks out into the bloodstream, causing elevated levels.
71
When does lipase peak in acute pancreatitis?
Lipase peaks within 4 to 8 hours after the onset of acute pancreatitis.
72
When does lipase typically decrease after an acute pancreatitis attack?
Lipase decreases within 8 to 14 days following the attack.
73
Is the increase in serum LPS activity proportional to the severity of the attack
No, it’s not necessarily proportiona
74
How does a reduced glomerular filtration rate affect serum LPS activity?
It increases serum LPS activity
75
Besides acute pancreatitis, in what other conditions does lipase elevate?
Lipase also elevates in penetrating duodenal ulcers, perforated peptic ulcers, intestinal obstruction, and acute cholecystitis.
76
What methods are employed for assessing lipase?
Methods include titrimetric, turbidimetric, spectrophotometric, fluorometric, and immunologic techniques
77
How do titrimetric methods assess lipase activity?
In titrimetric methods, LPS catalyzes the hydrolysis of fatty acids from an emulsion of olive oil or oleic acids. The liberated fatty acids are then titrated with dilute alkali, and the amount of alkali used over time serves as a measure of fatty acid produced during the reaction.
78
Explain turbidimetric methods to determine LPS activity?
The ΔA/min at 340 nm absorbance after hydrolysis of fatty acids from an emulsion of oleic acid is taken as a measure of LPS activity.
79
How do turbidimetric and titrimetric assays compare in terms of simplicity and speed
Turbidimetric methods are simpler and more rapid than titrimetric assays.
80
What substrates and systems are used in spectrophotometric methods?
Many substrates and complex auxiliary and indicator systems are employed.
81
How does LPS hydrolyze synthetic 1-oleoly-2,3-diacetylglycerol in alkaline conditions?
It produces an unstable dicarbonic acid ester.
82
What color is detectable at 540 nm during LPS hydrolysis?
A bluish purple color due to the hydrolysis of dicarbonic ester to glutaric acid and methylresorufin.
83
What is the relationship between the rate of color formation and LPS activity
The rate of color formation is directly proportional to LPS activity.
84
What are the advantages of turbidimetric methods over titrimetric assays?
Turbidimetric methods are simpler and faster.
85
What specific wavelength is used to read absorbance in turbidimetric methods?
340 nm
86
What type of fatty acids are hydrolyzed in titrimetric methods?
Fatty acids from an emulsion of olive oil or oleic acids.
87
What serves as a measure of fatty acid production in titrimetric methods?
The amount of alkali used over time.
88
What is the main principle behind spectrophotometric methods for LPS assessment?
Color formation due to the hydrolysis of synthetic 1-oleoly-2,3-diacetylglycerol.
89
What is the primary outcome measured in spectrophotometric assays?
The rate of color formation, which reflects LPS activity.
90
What are the limitations of using LPS activity as a marker for disease severity?
LPS activity may not always correlate directly with disease severity.
91
How can immunologic techniques be employed to assess LPS activity?
Immunologic techniques use antibodies to specifically detect LPS.
92
What are the potential sources of error in spectrophotometric LPS assays?
Interference from other substances or variations in sample preparation
93
what does increase in amylase indicate
acute pancreatitis
salivary gland inflammation
94
What is the function of amylase (AMY) in the breakdown of starch and glycogen?
Amylase catalyzes the hydrolysis of starch and glycogen into smaller sugar molecules, such as maltose and glucose.
95
How does AMY catalyze the hydrolysis of 1,4-α-glycosidic linkages in polysaccharides?
Amylase breaks down the glycosidic bonds between glucose units by adding water molecules, resulting in the release of individual sugar molecules.
96
Why is calcium essential for the functional integrity of AMYs?
AMYs are calcium metalloenzymes, meaning they require calcium ions for their proper structure and enzymatic activity.
97
Which ions are the most effective activators of amylase?
Chloride and bromide ions are known to be the most effective activators of amylase.
98
How does S-type amylase differ from P-type amylase in terms of secretion and activity?
S-type amylase is secreted by the salivary glands and is active in the oral cavity. P-type amylase, secreted by the pancreas, becomes active in the small intestine.
99
How can amylase pass through the glomeruli of the kidney?
Amylase has a molecular weight of 54,000 to 60,000 Da, allowing it to pass through the glomerular filtration barrier in the kidney.
100
Where is the greatest concentration of active S-type amylase noted, and what role does it play there?
The salivary glands have the highest concentration of active S-type amylase. It plays a crucial role in initiating starch digestion in the mouth.
101
How is S-type amylase affected by gastric acid?
Gastric acid inactivates S-type amylase, rendering it ineffective in the acidic environment of the stomach.
102
Apart from salivary glands, where else is AMY activity present in the body?
AMY activity is also found in muscles, lungs, semen, testes, ovaries, and fallopian tubes
103
Why is serum and urine AMY predominantly of salivary and pancreatic origin?
Serum and urine AMY mainly originate from salivary glands and the pancreas, which are the primary sources of this enzyme in the body.
104
What is the clinical significance of amylase
Amylase levels increase within 5 to 8 hours of symptom onset in acute pancreatitis and salivary gland inflammation
105
Why is P-AMY preferred over total enzyme activity for patients with acute abdominal pain?
Due to lack of specificity, P-AMY provides a more accurate measure in such cases.
106
What other condition, besides acute pancreatitis, can lead to an increase in amylase levels?
Salivary gland inflammation.
107
How much can serum P-AMY activity elevate in cases of biliary tract diseases like cholecystitis?
Up to four-fold elevation.
108
What enzyme measurement is particularly useful for patients experiencing acute abdominal pain?
P-AMY instead of total enzyme activity due to its specificity.
109
How does biliary tract disease affect serum P-AMY activity
Biliary tract diseases, such as cholecystitis, cause up to a four-fold elevation in serum P-AMY activity.
110
When does the increase in amylase levels typically occur during acute pancreatitis?
Within 5 to 8 hours of symptom onset
111
What happens to amylase levels during salivary gland inflammation?
They increase within 5 to 8 hours of symptom onset.
112
Is total enzyme activity a reliable measure for patients with acute abdominal pain
No, due to lack of specificity, P-AMY is used instead for more accuracy.
113
How is amylase related to biliary tract disease such as cholecystitis?
Biliary tract disease can cause up to a four-fold elevation in serum P-AMY activity.
114
What are chromogenic methods used for in determining alpha-amylase activity?
Chromogenic methods use a starch substrate to which a chromogenic dye has been attached, forming an insoluble dye–substrate complex.
115
What happens to the dye–substrate complex when AMY hydrolyzes the starch substrate?
As AMY hydrolyzes the starch substrate, smaller dye–substrate fragments are produced, and these become water-soluble.
116
How is the increase in color intensity related to AMY activity in chromogenic methods?
the increase in color intensity of the soluble dye–substrate solution is proportional to AMY activity.
117
What alternative method has been used recently to determine AMY?
Coupled enzyme systems have been used to determine AMY
118
Describe the continuous monitoring technique used in determining AMY activity.
Based on a continuous monitoring technique, the change in absorbance of NAD+ at 340 nm is measured.
119
What is the purpose of using a chromogenic dye in alpha-amylase assays?
The chromogenic dye allows visual or spectrophotometric detection of the enzymatic reaction, providing a measurable signal.
120
Why is the change in absorbance at 340 nm relevant in AMY determination?
The change in absorbance at 340 nm corresponds to the enzymatic reaction involving NAD+ and provides a quantitative measure of AMY activity.
121
How does the formation of the insoluble dye–substrate complex aid in AMY detection?
The insoluble complex allows separation of the unreacted dye from the reaction products, facilitating accurate measurement of the enzymatic activity.
122
What is the significance of water solubility in the dye–substrate fragments produced during AMY hydrolysis?
Water solubility ensures that the fragments can be easily detected and quantified, reflecting the extent of AMY activity.
123
What advantages does the continuous monitoring technique offer over other methods for AMY determination?
The continuous monitoring technique provides real-time data and allows dynamic measurement of AMY activity, making it more sensitive and informative.
124
Why is heparinezed sample preferable for sample collection of amylase
Heparinized sample is recommended for AMY activity because all other anticoagulants inhibit AMY activity
125
serum reference interval for serum amylase
31 to 107 U/L
126
mention the liver function tests
Alanine aminotransferase (ALT)
Aspartate aminotransferase (AST)
γ-glutamyltransferase (GGT)
Alkaline phosphatase (ALP)
5′-nucleotidase
127
What are the clinically common alterations in liver enzyme activities?
Clinically common alterations include hepatocellular damage and cholestasis, along with certain liver diseases displaying a mixed biochemical picture.
128
Which enzyme activities are elevated during hepatocellular damage?
Hepatocellular damage is associated with elevated transaminase and glutamate dehydrogenase activities.
129
Which enzyme activities indicate cholestasis
Cholestasis is characterized by elevated alkaline phosphatase, 5′- nucleotidase, and γ-glutamyltransferase activities.
130
What are the clinically common alterations in liver enzyme activities
Clinically common alterations include hepatocellular damage and cholestasis, along with certain liver diseases displaying a mixed biochemical picture.
131
Which enzyme activities are elevated during hepatocellular damage?
Hepatocellular damage is associated with elevated transaminase and glutamate dehydrogenase activities.
132
Which enzyme activities indicate cholestasis
Cholestasis is characterized by elevated alkaline phosphatase, 5′- nucleotidase, and γ-glutamyltransferase activities.
133
What is the role of Pyridoxal-5′-phosphate (P-5′-P) in amino group transfer?
P-5′-P accepts the amino group from aspartate or alanine.
134
What are the first reaction products when P-5′-P accepts an amino group from aspartate or alanine
The first reaction products are oxaloacetate or pyruvate, respectively.
135
How is glutamate formed in the process involving Pyridoxamine-5′ phosphate?
Pyridoxamine-5′ phosphate transfers its amino group to 2-oxoglutarate, forming glutamate.
136
Where are AST and ALT enzymes found in the body?
AST and ALT are found in the heart, liver, skeletal muscle, and kidney, with lesser amounts in the heart and skeletal muscle.
137
What is the most significant cause of an increase in serum transaminase activity?
Liver disease is the most significant cause of increased serum transaminase activity.
138
How does ALT activity compare to AST in various liver conditions?
ALT activity is generally higher than that of AST, except in cases of alcoholic hepatitis, hepatic cirrhosis, and liver neoplasia
139
When do serum AST and ALT activities elevate in acute hepatic necrosis
Serum AST and ALT activities increase before the clinical signs and symptoms of acute hepatic necrosis appear.
140
What level of elevation occurs in acute liver disease relative to the upper reference limit?
Acute liver disease can result in a 10 to 40-fold elevation above the upper reference limit.
141
What threshold of aminotransferases is efficient for diagnosing acute liver injury?
The most efficient threshold for diagnosing acute liver injury is at 7-fold the upper limit.
142
How is chronic hepatitis diagnosed concerning ALT levels?
A persistence in ALT increase for 6 months is used to diagnose chronic hepatitis.
143
Besides viral and alcoholic hepatitis, what is the most common cause of aminotransferase increases
Nonalcoholic fatty liver disease is the most common cause of aminotransferase increases.
144
What effect does liver carcinoma have on enzyme levels?
Liver carcinoma causes a 2-fold increase in both AST and ALT enzymes.
145
Which hormone stimulates glycogenolysis in the liver?
Glucagon stimulates glycogenolysis.
146
What is the significance of PSA in disease detection?
PSA (Prostate-Specific Antigen) is used for detecting prostate gland conditions, both benign and diseased.
147
Which enzyme is elevated in primary or secondary liver cancer
Alkaline phosphatase shows elevated levels in liver cancer.
148
In which cancers have elevations in CK1 been demonstrated?
CK1 elevation has been observed in prostate cancer and small cell carcinoma of the lung.
149
What is LD, and how is it related to cancer?
LD (Lactate Dehydrogenase) is an enzyme. It has been demonstrated to be elevated in several types of cancers.
150
List the cancers where an elevation of LD has been observed.
Liver cancer, Non-Hodgkin’s lymphoma, acute leukemia, non-seminomatous germ cell testicular cancer, seminoma, neuroblastoma, and other carcinomas (such as breast, colon, stomach, and lung cancer).
151
How is the elevation of prostatic acid phosphatase (PAP) associated with prostate cancer?
An elevated level of PAP is strongly linked to prostate cancer.
152
How can LD levels be used in diagnosing liver cancer or non-Hodgkin’s lymphoma?
Elevated LD levels may serve as a diagnostic marker for these cancers.
153
Discuss the role of LD in non-seminomatous germ cell testicular cancer and seminoma.
LD elevation is observed in both non-seminomatous germ cell testicular cancer and seminoma
