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MLSCI360 > (NOT IN CSMLS?) SERUM ENZYMES > Flashcards

(NOT IN CSMLS?) SERUM ENZYMES Flashcards

1
Q

Describe the function and properties of enzymes

A
  • proteins that lower activation energy
  • catalyze chemicals reactions without being destroyed/ consumed
  • there is a relationship between enzyme, substrate, E-S complex, and product
  • affected by optimal pH and temperatures
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2
Q

Describe zero and first-order kinetics

A

Zero Order:
- used in measurement of enzyme activity
- dependent on [enzyme]
- complete saturation of enzymes and excess substrate
- reaction velocity Vmax is reached

First Order:
- proportional to [substrate]
- reaction rate reflects the amount of E-S complex formed

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3
Q

Compare fixed point vs continuous monitoring (kinetic) methods

A

Fixed Point:
- incubated at a set time and temperature, the reaction is stopped, change in absorbance is measured
- assumes reaction is constant and linear over time and follows zero order kinetics

Continuous Monitoring/ Kinetics:
- incubated at a set time and temperature, and change in absorbance is measured at multiple time points/ continuously until reaction is stopped
- verifies constant linear reaction rate
- preferred; shorter reaction time and ability to verify zero order kinetics

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4
Q

Differentiate competitive, Non-competitive, and uncompetitive inhibition

A

Competitive:
- inhibitor is a structural analog of substrate for the active site
- more substrate can be added to reach Vmax to avoid inhibition
- appearance of increased Km when there isn’t
- reversible

Non-Competitive:
- ie. metallic ion binds to allosteric site and causes conformational change
- Vmax cannot be reached

Uncompetitive:
- inhibitor binds to E-S complex and prevents formation of product
- adding more substrate worsens inhibition bc amount of E-S is increased
- decreased Vmax and decreased Km
- reversible

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5
Q

Tissue Distribution of ALP

A

Intestine, liver, bone, placenta, RBC surfaces
- osteoblasts and hepatocytes

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6
Q

A 10°C increase in temperature doubles the __ of enzyme

A

A 10°C increase in temperature doubles the reaction rate of enzyme

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7
Q

Clinical Significance of ALP

A
  • bone development in children (increased levels)
  • placental ALP elevated in last trimester of pregnancy
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8
Q

Diseases from increased ALP

A
  • Bone disease (paget’s disease, hyperparathoidism, osteoporosis)
  • Hepatobiliary disease, hepatic cancer, hepatitis, cirrhosis
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9
Q

Activators and Inhibitors of ALP

A

Activators: Zn2+, Mg2+
Inhibitors: phosphate, anticoagulants (oxalates, citrate, EDTA)

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10
Q

Limitations of ALP

A
  • serum or heparin plasma measured within 4 hours
  • ALP falsely increases when stored at 4°C and RT
  • HEMOLYSIS
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11
Q

Tissue Distribution of LD

A
  • non-specific; throughout body
  • highest in heart, liver, skeletal muscles, RBCs, platelets, lymph nodes
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12
Q

Clinical Significance of LD

A
  • non-specific indicator of disease
  • anemia, liver disease, heart disease
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13
Q

Disease of increased LD

A
  • anemia (hemolytic, megaloblastic)
  • liver disease (not as specific as GGT or ALT)
  • heart disease (not as specific as troponins)
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14
Q

Coenzyme of LD

A

NAD+

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15
Q

Limitations of LD

A
  • serum is preferred: platelets in plans can increase LD levels
  • serum must be stored at RT
  • some LD isoenzymes are cold labile
  • HEMOLYSIS
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16
Q

ALT Tissue Distribution

A
  • primarily liver and kidneys
17
Q

Clinical Significance of ALT

A
  • hepatic disease
18
Q

Coenzyme of ALT

A

Pyridoxal 5’ phosphate (vitamin B6)

19
Q

Limitations of ALT

A
  • unstable; must be measured within 24 hrs
  • stable at -70°C
  • HEMOLYSIS; due to endogenous LD enzyme
20
Q

Tissue Distribution of GGT

A
  • kidney, bile ducts of liver, pancreas and intestine
21
Q

Clinical Significance of GGT

A
  • indicator if hepatobiliary disease (biliary obstruction)
  • elevated in alcohol use, and liver cancer
  • determines whether ALP elevation is due to hepatobiliary disease (increased GGT) or skeletal disease (normal GGT)
22
Q

Activator and Inhibitors of GGT

A

Activator: Mg2+
Inhibitor: citrate, oxalate, fluoride

23
Q

Limitations of GGT

A
  • serum and plasma samples are stable at 4°C
  • preferably non-hemolyzed
  • increased GGT in newborns
  • false increase due to drugs (ethanol, warfarin, phenobarbital, phenytoin)
24
Q

CK Tissue Distribution

A
  • skeletal muscle, heart, brain
25
Q

Clinical Significance of CK

A
  • assessing muscle disease and heart disease
26
Q

Diseases of increased CK

A
  • muscle (muscular dystrophy, rnhabdomylosis)
  • heart (myocardial infarction, but cardiac troponins are more specific)
27
Q

Activator, coenzyme, and inhibitors of CK

A

Activator: Mg2+
Coenzyme: ATP
Inhibitors: all anticoagulants besides heparin (Mn2+, Ca2+, Zn2+, excess Mg2+)

28
Q

Limitations of CK

A
  • serum and heparin plasma specimens are stable up to 48hrs at 4°C
  • HEMOLYSIS; interferes with second hexokinase reaction
29
Q

Amylase Tissue Distribution

A
  • salivary glands, pancreas, ovaries, fallopian tubes, and lungs
30
Q

Clinical Significance of Amylase

A
  • increased in gland inflammation (mumps virus), and other intra-abdominal disorders (acute pancreatitis*, biliary tract disease, appendicitis, ectopic pregnancy)

*lipase is more specific for acute pancreatitis

31
Q

Activator and Inhibitors to Amylase

A

Activator: Ca2+ absolutely required
Inhibitors: all anticoagulants EXCEPT heparin

32
Q

Limitations of Amylase

A
  • Serum and urine amylase stable at RT
  • In vitro, plasma triglycerides inhibit amylase activity
  • Morphine and opiates elevate amylase
33
Q

Lipase Tissue Distribution

A
  • pancreas, stomach, and small intestine
34
Q

Clinical Significance of Lipase

A
  • used to diagnose acute pancreatitis
  • also increased in gastric/ duodenal ulcers and intestinal obstruction
35
Q

Cofactors of Lipase

A
  • Colipase and bile salts
36
Q

Limitations of Lipase

A
  • stable in serum at RT for one week
  • HEMOLYSIS; hemoglobin inhibits lipase activity
  • bilirubin and lipemia interference is method dependent

MLSCI360 (22 decks)

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