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CHEM EXAM 4 > ENZYMES > Flashcards

ENZYMES Flashcards

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1
Q

factors that influence and enzyme reaction

A
  • substrate concentration
  • enzyme concentration
  • pH
  • temperature
  • co-factors
  • inhibitors
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2
Q

Two general methods used to measure an enzyme activity

A
  • fixed time

- continuous-monitoring or kinetic assay

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3
Q

fixed time measurements

A
  • reactants ( and pt sample) are combined
  • RXN proceeds for a defined period of time
  • rxn is stopped(inactivate the enzyme)
  • measurement of some chromogen is made
  • RXN assumed to be linear over measurment time, so the greater the rxn, the more enzyme present
  • non linear may occur
    • at high activities with substrate depletion
    • during lag phase which may vary from sample
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4
Q

Continuous-monitoring

A

multiple measurements during reaction

  • usually absorbance changes
  • specific intervals or continuously
  • advantages
    • linearity of the reaction can be adequate verified
    • background color has minimal effect since a change is abs is measured
    • can recognize and compensate for lag phase
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5
Q

How to measure macramylasemia

A

by precipitating with a high MW polymer and remeasuring or measure urine amylase. If serum is elevated but urine is normal, suggestive if macroamylase.

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6
Q

specificity of Enzymes used to assess acute pancreatitis

A

increase amylase and Lipase

- lipase is more clinically specific

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7
Q

G-6-PDH

A

is an RBC enzyme

  • decreased levels are signigicant
  • deficiency in hemolytic anemia, anti-malarial drug promaquine
  • use blood
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8
Q

GGT in liver vs bone

A

metabilized by the liver

  • useful in accessing liver disease in adults
  • distinct isoezymes found in liver and bone
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9
Q

Enzyme most sensitive alcohol intake

A

GGT

- used to monitor chronic alcohol abuse

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10
Q

Applications for acid phosphatase

A

historically used as a prostate cancer marker

- used for an indication of late stage prostate cancer

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11
Q

pseudocholinesterase

A
  • decrease levels are significant
  • used to monitor pesticide exposure
  • decreased in liver disease
  • prolonged apnea
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12
Q

muscle enzymes

A
  • creatinine kinase
  • aldolase
  • LDH
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13
Q

Liver Enzymes

A
  • ALT
  • AST
  • ALP
  • GGT and 5’ nucleotidease
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14
Q

Pancreatic Enzymes

A

amylase

lipase

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15
Q

Miscellaneous enzymes

A
  • acid phosphatase
  • cholinesterase
  • Gluc-6-Phose dehydrogenase
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16
Q

Creatine Kinase

A

-skeletal/heart muscle and brain tissue
- normal less than 200 F, less than 300 M
- elevated AMI, Duchenne muscular dystrophy
- seen in muscle wasting disease
- hypothryroidism, polymyotisis
- flourescent detection of CK
-measures with a 3 step-coupled- reaction
- has lag phase
- NADPH is flourescent
- CK is unstable due to to disulfide bonds
-

17
Q

CK isozymes

A

bb= brain- fast moving
mb= heart- intermediate
mm- skeletal muscle

18
Q

Aldolase

A

muscle enzyme occas. with CK

  • not assayed in many labs
  • reference ranges vary (age dependent)
  • very sensitive to hemolysis due to high aldolase in RBCs
  • 2-step reaction causing involving NADH using Fructose-1-6-phosphate
19
Q

LD or LDH

A

increased in many disorders
- liver disease, muscle trauma, renal infart, hemolytic disease, pernicious anemia
-in MI “flipped isoenzyme”
- increased longer than CK in a MI
has 4 subunits
- assays are hemolysis sensitive
- shaking and partially filled tube problems
-assay has a forward reaction that results in NADH
- reverse reaction is 3x more sensitive to

20
Q

LD isoenzyme patterns in disease states

A

MI: “ flipped” LD1>LD2
LD5 elevated skel. muscle or liver disease
central fractions elevated:
- lung sources or possibly some malignancy
- central fraction elevations usually not diagnositc
- all fractions elevated: shock, sepicemia

21
Q

AST

A

liver, heart, skeletal muscle, RBC

  • primarily used for diagnosis of liver disorders
  • elevated in MI
  • increased in 24-48 hours
  • measured with an AST assay- measures absorbance decrease at 340 nm
  • pryridoxal-5-phosphate cofactor
22
Q

Isoenzymes of LD

A 
LD1-HHHH-heart,RBC, kidney
LD2-MHHH- heart
LD3- MMHH- lung
LD4-MMMH- many tissues
LD5- MMMM- skeletal muscle and liver
23
Q

Diagnosis of an MI

A

MI first CK increases, then AST and then LD

24
Q

ALT

A

found in the liver with lesser amount in the heart and skeletal muscle

  • used to diagnose liver disease
  • less sensitive to hemolysis than AST
  • measured with a couples reaction involving NADH
  • both ALT and AST are included with a standardized pane; (Comprehensive Metabolic Profile)
25
Q

Alkaline Phosphate (ALP)

A

routinely included in chemistry panels

  • found bound to cell membranes
  • found in the liver, placenta and bone
  • has isoenzymes found in liver, bone placenta and intestine. 45% liver, 45% bone, 5% intestine
26
Q

Elevated ALP

A
  • cholestasis/obstructive liver disease
  • bone disease: osteoblastic increased in Pagets disease
  • intestinal infarction
  • placenta -like ALP- tumor marker, malignacy. third trimester in pregnancy
27
Q

Fractionation of ALP isoenzymes

A
  • electrophoresis in liver,bone,intestinal and placental fractions visualized
  • heat stablility: 56 deg for 10 mins
  • placenta: heat stable
  • bone heat liable
  • liver/intestinal: intermediate stability
28
Q

Measuring of ALP

A

P-nitrophenol absorbs at 405- 415

  • Mg is a cofactor
  • not hemolysis sensitive
29
Q

GGT

A
  • measure rate reaction using substrate which liberates p-nitrophenol
  • not hemolysis sensitive
  • elevated in billiary tract obstruction, pancreatic cancer
  • useful in liver disease
  • drugs metabolized in the liver may elevate GGT
30
Q

5’ nucleotidase

A

clinically significant in the same manner in GGT

  • elevated in liver and billiary tract
  • more difficult to assay
  • helpful in differentiating an elevated ALP whether due to liver or bone disease
31
Q

Amylase

A

breaks down starches into simpler sugars and maltose
- low MW enzyme- present in both serum and urine
- found in Saliva and Panreas and give rise to S-type and P-type isozymes
- used to diagnose acute pancreatitis
-rises after attack, peaks at 24 hr
- decreases gradually
OTHER:
- elevated in parotid gland disorders(mumps), renal insufficency, DM due to salivary isoenzyme
- elevated in Macroamylsemia
-

32
Q

Amylase assys

A

amyloclastic: starch and iodine reaction
saccharogenic: sugars produced upon action of amy-on starch
- serum stable at room temp
- requires chloride ion
- urine enzyme liable at acidic pH of urine
- ration urine amylase to urine creatinine using spot urine

33
Q

Lipase

A

Hydrolyzes fats to produce fatty acids and glycerol

  • used to diagnose acute pancreatitis
  • greater clinical specificity to acute pancreatitis than amylase
  • amylase and lipase frequently ordered together
34
Q

Acute pancreatitis

A

increased Amylase and lipase

35
Q

Acid Phosphate

A

usually measures same reaction as ALP but assay at acidic

  • stabilize at acid pH
  • greatest concentrations in prostate, liver, spleen and bone
  • high levels used to detect semen in suspected rape cases(vaginal washings)
36
Q

Cholinesterases

A

decreased levels are significant

  • RBC enzymes known as acetylcholinesterase make hemolysate and assay : used for monitoring pesticide exposure
  • Pseudocholinesterase(serum/plasma)
  • pesticide exposure

CHEM EXAM 4 (1 decks)

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