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Clinical Chemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Enzymes

A

proteins that act as biological catalysts
decrease delta G to facilitate reaction
normally inside the cells; only in blood when cells are damaged

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2
Q

Enzyme reaction factors

A 
time
substrate level
pH of mixture
temperature
enzyme concentration
activators/inhibitors that may be present
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3
Q

Inhibitors

A

competitive- binds to enzyme active site
uncompetitive- binds to ES complex
non-competitive - binds to other site & causes conformational change
reversible : can ‘dilute’ off
non reversible : alters active site permanently

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4
Q

Time

A

fixed or kinetic (series of times)

product formation different depending on the time

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5
Q

substrate

A

goal is to make so much substrate available so that it does not become a limiting factor & makes all the reactions a zero order reaction time

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6
Q

pH of mixture

A

most rx use pH of 7-8

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7
Q

temperature

A

optimume 37 in US; 30 in europe

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8
Q

enzyme concentration

A

originate from patient samples

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9
Q

activators/inhibitors

A

activators aid enzyme reaction to be optimum

inhibitors compete & reaction is not optimum (drugs in patient’s system etc)

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10
Q

Km

A

substrate concentration at half of Vmax

exceeding Km will give you a zero order reaction

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11
Q

Enzyme class names

A 
oxidoreductases - lactic dehydrogenase
transferases
hydrolases
lyases
isomerases
ligases
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12
Q

International Unit (IU)

A

the amount of enzyme which can convert 1 umol of substrate per minute to product

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13
Q

Systemic Unit (SI)

A

katal unit - amount of enzyme that catalyzes 1 mole of substrate per second

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14
Q

Isoenzymes

A

forms of an enzyme that are molecularly different but catalyze the same reaction
can usually be separated by electrophoresis or Ab-Ag reaction

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15
Q

Creatine Kinase

A

associated with ATP regeneration in muscle & transport systems
found in heart, muscle, & brain tissue
elevated CK associated with AMI, muscular dystrophy, CNS seizures etc etc etc

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16
Q

CK analyzer forward reaction

A

forward reaction
creatine + ATP w/ patient’s CK -> CrP + ADP
ADP + PEP –(PEP phophatase) –> ATP + pyruvate
pyruvate + NADH +H –(LD)-> lactate & NAD
NAD IS READ AT 340 nm

17
Q

CK analyzer reverse rx

A 
CrP + ADP --(CK)--> creatine + ATP 
ATP + glucose --(HK)--> G-6-P + ADP
G-6-P + NADP --(G6PD)-> bleh + NADPH
more commonly used
CK is from patient sample!
doesn't take as much activation energy for this reaction & works better on most machines
18
Q

CK isoenzymes

A

M & B units in dimers - 3 isoforms
CK1 (BB)- brain tissue ; not usually found in serum
CK2 (MB) - heart muscle, increases 4-8 hr after AMI then normal after 48-72 hrs
CK3 (MM) - skeletal muscle, increases in muscle diseases

19
Q

Aspartate Aminotransferase (AST)

A

transfers amino acid groups to make a new amino acid
coenzyme pyrioxal phosphate (vit B6)
found in cardiac, liver & skeletal tissue
SIGNIFICANT in viral hepatitis

20
Q

AST analyzer methods

A

uses amino acid transferase reaction
substrate: L-aspartate
enzymes used: AST (patient’s) & malate dehydrogenase
reads NAD @ 340 nm

21
Q

LD analyzer method

A

uses pyruvate to lactate & the change in the coenzyme NAD
pyruvate + NADH + H -(LD)–> lactate + NAD
reaction read at 340 nm
enzyme found only in the CYTOPLASM of cells

22
Q

LD isoenzymes

A

uses H & M subunits in tetramers
heart attack see LD1> LD2 (flipped from normal)
LD4 & LD5 increase in liver issues
LD3 -pulmonary

23
Q

after suspected heart attack what tests are usually ordered?

A

general lab tests to see if lungs, kidneys & systems are normal
specific tests: CK, AST, LD, & Troponin

24
Q

tests ordered when liver involvement suspected

A

AST, LD, ALT, gamma -GT, ALP

25
Q

Alanine Transferase (ALT)

A

found more in the liver than other tissues
viral hepatitis: ALT may increase 5-10x
liver cirrhosis: AST> ALT (usually less than 5x)

26
Q

ALT analyzer method

A 
amino transferase enzyme 
substrate: L-alanine
ALT: patient enzyme
2nd enzyme: LD
measure: NAD @ 340nm
27
Q

Alkaline phosphatase (ALP)

A

NEEDS MG2+ as ACTIVATOR
found in most cell membranes as it is involved in the transfer of metabolites across cell membranes
ALP in serum: bone & liver

28
Q

ALP associations

A

^^ ALP associated w/ liver or bone
liver biliary duct obstructions can lead to ^ ALP
bone diseases ^ ALP : ricketts, bone cancer, padgetts
hepatitis: modest ^ ALP

29
Q

ALP method

A

ALP is a hydrolase enzyme
substrate:para-nitro-phenol phosphate (PNPP)
ALP: patient enyzme
turns yellow & read

30
Q

ALP isoenzymes

A

5 possible isoenzymes
liver isoenzyme overlaps w/ bone isoenzyme
bone isoenzyme is not as heat stable as liver isoenzyme - heat stability isoenzyme separation technique

31
Q

Gamma glutaryl transferase (Gamma-GT)

A

involved in the transfer of gamma-glutamyl group to other amino acid
found in all cells but muscle
recent alcohol consumption will falsely elevate GGT levels
not used very commonly

32
Q

Amylase

A

found in salivary gland & pancreas
hydrolyzes a-1,4-glycosidic bonds ; functions to break up complex CHO
major increases in amylase in pancreatitis & mumps

33
Q

Amylase methods

A

classic iodometric method
saccharogenic method
enzymatic methods: uses artificial maltose & measures NADH from patient amylase

34
Q

Lipase

A

only pancreatic enzyme; breaks off fatty acids from triglycerides
stays elevated longer than amylase in pancreatitis
substrate: triolein
enzyme: patient lipase
measures dye color change

35
Q

Amylase Reaction

A

substrate: maltose
patient enzyme: amylase
other enzymes: a-glucosidase, hexokinase, G6PD,
Read: NADH

Clinical Chemistry (23 decks)

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