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Clinical Chemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Enzyme (mechanism of action)

A
  • catalysts (not consumed in rxns)
  • decrease activation energy needed to form product for more rapid formation
  • S + E –> ES –> P + E
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2
Q

Factors affecting enzyme reactions

A
  • time: fixed or kinetic
  • substrate level
  • pH of mixture (pH 7-8)
  • temperature (30-37C)
  • enzyme concentration
  • activators/inhibitors
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3
Q

competitive inhibitors

A

bind to active site of enzyme

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4
Q

uncompetitive inhibitors

A

bind to ES complex

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5
Q

non-competitive inhibitors

A

bind to another site (not active site) on enzyme

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6
Q

Enzyme classes

A
  • oxidoreductases
  • transferases
  • hydrolases
  • lyases
  • isomerases
  • ligases
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7
Q

Enzyme unites of measure

A
  • international unit (amt of enzyme which can convert 1 umole of substrate to product per min)
  • systemic unit (amt of enzyme that catalyzes 1 mole of substrate per second = katal unit)
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8
Q

isoenzymes

A
  • forms of enzymes that are only structurally different
  • can catalyze same reaction as enzyme
  • separated by electrophoresis or Ag-Ab rxn
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9
Q

Creatine kinase

A
  • associated with ATP regeneration in muscle and transport systems
  • found in heart, muscle, brain tissue
  • elevations associated with AMI, muscular dystrophy, CNS seizures/shock, hypothyroidism, Reye’s syndrome, malignant hyperpyrexia
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10
Q

CK methods

A
  • forward rxn: measure absorbance

- reverse rxn: commonly used method

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11
Q

CK isoenzymes

A
  • M and B units of dimer
  • CK1 or BB isoenzyme (brain)
  • CK2 or MB isoenzyme (heart muscle)
  • CK3 or MM isoenzyme (skeletal muscle)
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12
Q

Aspartate Aminotransferase (AST)

A
  • transfers amino group to make new AA
  • pyridoxal phosphate is coenzyme
  • found in cardiac, liver and skeletal tissue
  • significant in viral hepatitis
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13
Q

AST methods

A
  • amino acid transferase rxn with alpha keto acid oxoglutarate
  • read NAD absorbance
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14
Q

LD method

A
  • uses pyruvate to lactate
  • NAD absorbance is read
  • increases of LD only if cell damage (because its a cytoplasmic enzyme)
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15
Q

LD isoenzymes

A
  • uses H and M subunits in tetramers
  • 5 possible isoenzymes
  • LD1 > LD2 in heart attack
  • LD4 and LD5 increase in liver disease
  • LD3 is seen in pulmonary disorders
  • LD6 is alcohol dehydrogenase
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16
Q

Lactate Dehydrogenase

A
  • In AMI: rise, peak, remain elevated for 10 days

- in hepatic disorders: LD5 increase

17
Q

Heart attack tests

A

CK, AST, LD and troponin

18
Q

Liver disease tests

A

AST, LD, ALT, gamma-GT, ALP

19
Q

Alanine Transferase (ALT)

A
  • found in liver (liver specificity)
  • increases in viral hepatitis, so does AST
  • in cirrhosis AST > ALT
20
Q

ALT method

A
  • rxn is AA transfer from alaning to keto acid oxoglutarate

- read NAD absorbance

21
Q

Alkaline Phosphatase (ALP)

A
  • hydrolyzes phosphate groups from molecules at alkaline pH
  • Mg is activator
  • found in most cell membranes
  • found in intestine, kidney, bone, liver and placenta
  • increases associated with liver or bone
22
Q

ALP method

A
  • ALP is hydrolase enzyme

- method uses para-nitro-phenol phosphate (PNPP)

23
Q

ALP isoenzymes

A
  • 5 isoenzyme forms
  • liver and bone overlaps on electrophoresis
  • do immunochemical method for Bone ALP
  • inhibition testing uses phenylalanine
24
Q

Gamma-GT (Gamma glutaryl transferase)

A
  • involved in the transfer of gamma-glutamyl group to other AA
  • found in all cells but muscle
  • originates in hepatobiliary system
  • can increases with alcohol and cirrhosis
25
Q

Amylase

A
  • found in salivary glands and in pancreas
  • 3 isoenzymes for salivary amylase, 3 for pancreatic amylase
  • hydrolyzes alpha-1,4-glycosidic bonds
  • increase seen in pancreatitis, mumps
26
Q

Amylase methods

A
  • Classic iodometric method
  • Saccharogenic method
  • Enzymatic method
  • read absorbance
27
Q

Classic iodometric method (amylase)

A
  • iodine used to react with starch substrate

- when starch is all glucose, no iodine rxn

28
Q

Saccharogenic method (amylase)

A

measured glucose formed by amylase action on starch substrate

29
Q

Enzymatic method (amylase)

A

uses artificial substrate and measures glucose

30
Q

Lipase

A
  • pancreatic enzyme
  • used in conjunction with amylase to identify pancreatitis
  • method uses artificial substrate of triolein and links rxns to dye color change

Clinical Chemistry (8 decks)

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